1 UI - 385FV-0055 AU - Sacksteder CA AU - Kanazawa A AU - Jacoby ME AU - Kramer DM TI - The proton to electron stoichiometry of steady-state photosynthesis in living plants: A proton-pumping Q cycle is continuously engaged SO - Proceedings of the National Academy of Sciences of the United States of America 2000 Dec 19;97(26):14283-14288 IS - 0027-8424 MH - Steady-state electron and proton transfer MH - Chemiosmotic coupling MH - Cyclic electron transfer MH - Energy budget MH - Chlorophyll-a fluorescence MH - Photosystem-i MH - Quantum efficiencies MH - Spinach thylakoids MH - Absorbency changes MH - Flashing light MH - 2 photosystems MH - Intact plants MH - Green-algae MH - Pea leaves AB - A noninvasive technique is introduced with which relative proton to electron stoichiometries (H+/e(-) ratios) for photosynthetic electron transfer can be obtained from leaves of living plants under steady-state illumination, Both electron and proton transfer fluxes were estimated by a modification of our previously reported dark-interval relaxation kinetics (DIRK) analysis, in which processes that occur upon rapid shuttering of the actinic light are analyzed. Rates of turnover of linear electron transfer through the cytochrome (cyt) b(6)f complex were estimated by measuring the DIRK signals associated with reduction of cyt f and P-700 The rates of proton pumping through the electron transfer chain and the CF0-CF1 ATP synthase (ATPase) were estimated by measuring the DIRK signals associated with the electrochromic shifting of pigments in the light-harvesting complexes, Electron transfer fluxes were also estimated by analysis of saturation pulse-induced changes in chlorophyll a fluorescence yield. It was shown that the H+/e(-) ratio, with respect to both cyt b(6)f complex and photosystem (PS) II turnover, was constant under low to saturating illumination in intact tobacco leaves. Because a H+/e(-) ratio of 3 at a low light is generally accepted, we infer that this ratio is maintained under conditions of normal (unstressed) photosynthesis, implying a continuously engaged, proton-pumping Q cycle at the cyt b(6)f complex. [References: 88] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Kramer DM Washington State Univ, Inst Biol Chem 289 Clark Hall Pullman, WA 99164 USA Washington State Univ, Inst Biol Chem Pullman, WA 99164 USA 2 UI - 385FV-0110 AU - Beltran B AU - Mathur A AU - Duchen MR AU - Erusalimsky JD AU - Moncada S TI - The effect of nitric oxide on cell respiration: A key to understanding its role in cell survival or death SO - Proceedings of the National Academy of Sciences of the United States of America 2000 Dec 19;97(26):14602-14607 IS - 0027-8424 MH - Mitochondrial membrane potential MH - Apoptosis MH - Necrosis MH - Mitochondrial permeability transition MH - Induced apoptosis MH - S-nitrosylation MH - Inhibition MH - Necrosis MH - Oxygen MH - Activation MH - Mechanisms MH - Chain MH - Step AB - The mitochondrion is a key organelle in the control of cell death. Nitric oxide (NO) inhibits complex IV in the respiratory chain and is reported to possess both proapoptotic and antiapoptotic actions. We investigated the effects of continuous inhibition of respiration by NO on mitochondrial energy status and cell viability. Serum-deprived human T cell leukemia (Jurkat) cells were exposed to NO at a concentration that caused continuous and complete (similar to 85%) inhibition of respiration. Serum deprivation caused progressive loss of mitochondrial membrane potential (Delta psi (m)) and apoptotic cell death. In the presence of NO, Delta psi (m), was maintained compared to controls, and cells were protected from apoptosis. Similar results were obtained by using stauroporin as the apoptotic stimulus. As exposure of serum-deprived cells to NO progressed (>5 h), however, Delta psi (m), fell, correlating with the appearance of early apoptotic features and a decrease in cel viability. Glucose deprivation or iodoacetate treatment of cells in the presence of NO resulted in a collapse of Delta psi (m), demonstrating involvement of glycolytic ATP in its maintenance. Under these conditions cell viability also was decreased. Treatment with oligomycin and/or bongkrekic acid indicated that the maintenance of Delta psi (m), during exposure to NO is caused by reversal of the ATP synthase and other electrogenic pumps. Thus, blockade of complex IV by NO initiates a protective action in the mitochondrion to maintain Delta psi (m); this results in prevention of apoptosis. It is likely that during cellular stress involving increased generation of NO this compound will trigger a similar sequence of events, depending an its concentration and duration of release. [References: 48] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Moncada S Univ Coll London, Wolfson Inst Biomed Res Cruciform Bldg,Gower St London WC1E 6BT England Univ Coll London, Wolfson Inst Biomed Res London WC1E 6BT England Univ London Univ Coll, Dept Med, Cell Biol Grp London WC1E 6JJ England Univ Coll London, Dept Physiol London WC1E 6BT England 3 UI - 385FV-0138 AU - Salomon AR AU - Voehringer DW AU - Herzenberg LA AU - Khosla C TI - Understanding and exploiting the mechanistic basis for selectivity of polyketide inhibitors of F0F1-ATPase SO - Proceedings of the National Academy of Sciences of the United States of America 2000 Dec 19;97(26):14766-14771 IS - 0027-8424 MH - Malate-aspartate shuttle MH - Amino-acid substitutions MH - Tumor-cell-lines MH - Apoptosis inducer MH - Transformed-cells MH - Mitochondria MH - Apoptolidin MH - Oligomycin MH - Resistance MH - Patterns AB - Recently, a family of polyketide inhibitors of F0F1-ATPase, including apoptolidin, ossamycin, and oligomycin. were shown to be among the top 0.1% most cell line selective cytotoxic agents of 37,000 molecules tested against the 60 human cancer cell lines of the National Cancer Institute. Many cancer cells maintain a high level of anaerobic carbon metabolism even in the presence of oxygen, a phenomenon that is historically known as the Warburg effect. A mechanism-based strategy to sensitize such cells to this class of potent smart molecule cytotoxic agents is presented. These natural products inhibit oxidative phosphorylation by targeting the mitochondrial F0F1: ATP synthase. Evaluation of gene expression profiles in a panel of leukemias revealed a strong correlation between the expression level of the gene encoding subunit 6 of the mitochondrial F0F1 ATP synthase (known to be the binding site of members of this class of macrolides) and their sensitivity to these natural products. Within the same set of leukemia cell lines, comparably strong drug-gene correlations were also observed for the genes encoding two key enzymes involved in central carbon metabolism. pyruvate kinase, and aspartate aminotransferase. We propose a simple model in which the mitochondrial apoptotic pathway is activated in response to a shift in balance between aerobic and anaerobic ATP biosynthesis. Inhibitors of both lactate formation and carbon flux through the Embden-Meyerhof pathway significantly sensitized apoptolidin-resistant tumors to this drug. Nine different cell lines derived from human leukemias and melanomas, and colon, renal. central nervous system, and ovarian tumors are also sensitized to killing by apoptolidin. [References: 24] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Khosla C Stanford Univ, Dept Chem & Chem Engn MC5025 Stanford, CA 94305 USA Stanford Univ, Dept Chem & Chem Engn Stanford, CA 94305 USA Stanford Univ, Dept Genet Stanford, CA 94305 USA 4 UI - 385FV-0143 AU - Giraud E AU - Hannibal L AU - Fardoux L AU - Vermeglio A AU - Dreyfus B TI - Effect of Bradyrhizobium photosynthesis on stem nodulation of Aeschynomene sensitiva SO - Proceedings of the National Academy of Sciences of the United States of America 2000 Dec 19;97(26):14795-14800 IS - 0027-8424 MH - Aerobic phototrophic bacteria MH - Gram-negative bacteria MH - Reaction centers MH - Rhizobium-meliloti MH - Heme oxygenase MH - Strain btai-1 MH - Bacteriochlorophyll MH - Erythrobacter MH - Genes MH - Sandaracinobacter AB - Some leguminous species of the genus Aeschynomene are specifically stem-nodulated by photosynthetic bradyrhizobia. To study the effect of bacterial photosynthesis during symbiosis, we generated a photosynthesis-negative mutant of the Bradyrhizobium sp. strain ORS278 symbiont of Aeschynomene sensitiva. The presence of a functional photosynthetic unit in bacteroids and the high expression of the photosynthetic genes observed in stem nodules demonstrate that the bacteria are photosynthetically active during stem symbiosis. Stem inoculation by the photosynthetic mutant gave a 50% decrease in stem-nodule number, which reduced nitrogen fixation activity and plant growth in the same proportion. These results indicate an important role of bacterial photosynthesis in the efficiency of stem nodulation. [References: 39] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Giraud E INRA, Ecole Natl Agron Montpellier, Ctr Cooperat Int Rech Agron Dev,IRD, Lab Symbioses Trop & Mediterraneennes TA 10-J,Campus Baillarguet F-34398 Montpellier 5 France INRA, Ecole Natl Agron Montpellier, Ctr Cooperat Int Rech Agron Dev,IRD, Lab Symbioses Trop & Mediterraneennes F-34398 Montpellier 5 France CEA, Cadarache Dept Ecophysiol Vegetale & Microbiol, Lab Bioenerget Cellulaire F-13108 St Paul Durance France 5 UI - 385KD-0001 AU - Stahlberg R AU - Van Volkenburgh E AU - Cleland RE TI - Chlorophyll is not the primary photoreceptor for the stimulation of P-type H+ pump and growth in variegated leaves of Coleus x hybridus SO - Planta 2000 Dec;212(1):1-8 IS - 0032-0935 MH - Coleus x hybridus MH - Electric photoresponse MH - Leaf growth MH - Photosynthesis MH - Photomorphogenesis MH - P-type h+-atpase MH - Phaseolus-vulgaris l MH - Induced membrane hyperpolarization MH - Light-induced activation MH - Guard-cell protoplasts MH - Plasma-membrane MH - Pisum-sativum MH - Phytochrome-b MH - Leaf-cells MH - Vegetative development MH - Apoplastic ph AB - There has been persisting controversy over the role of photosynthesis in the stimulation of the plasma membrane Hf-ATPase and growth of dicotyledonous leaves by light. To investigate this, we compared the effects of light on growth, H+ net efflux and membrane potential (V-m) of strips which contained either only chlorophyll-free (white) mesophyll cells or chlorophyll-containing (green) cells cut from variegated Coleus leaves. White mesophyll cells responded to white, blue and red light with a hyperpolarization of V-m, an acidification of the apoplast and a promotion of growth, all of which began after a lag of 2-7 min. In contrast, green mesophyll cells showed a biphasic light response in which the hyperpolarization and the acidification were preceded by a rapid depolarization of V-m and an alkalinization of the apoplast. Nevertheless, green and white tissues showed comparable growth promotions in response to light. The light response of the leaf mesophyll is a composite of two separate photosystems. The initial depolarization and alkalinization are mediated by photosynthesis and blocked by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The slower hyperpolarization, acidification and growth response, on the other hand, are clearly in response to light absorption by pigments other than chlorophyll. [References: 46] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Stahlberg R Univ Washington, Dept Bot Box 355325 Seattle, WA 98195 USA Univ Washington, Dept Bot Seattle, WA 98195 USA 6 UI - 385KD-0009 AU - Crafts-Brandner SJ AU - Law RD TI - Effect of heat stress on the inhibition and recovery of the ribulose-1,5-bisphosphate carboxylase/oxygenase activation state SO - Planta 2000 Dec;212(1):67-74 IS - 0032-0935 MH - Gossypium (heat stress, rubisco) MH - Heat stress MH - Photosynthesis MH - Ribulose-1,5-bisphosphate carboxylase/oxygenase MH - Rubisco activase MH - Ribulose bisphosphate carboxylase MH - Rubisco activase MH - 1,5-diphosphate carboxylase MH - Spinach-chloroplasts MH - Leaf temperature MH - Light-activation MH - Photosynthesis MH - Sensitivity MH - Leaves MH - Inactivation AB - Experiments were conducted to determine the relative contributions of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) activation state vis-g-vis Rubisco activase and metabolite levels to the inhibition of cotton (Gossypium hirsutum L.) photosynthesis by heat stress. Exposure of leaf tissue in the light to temperatures of 40 or 45 degreesC decreased the activation state of Rubisco to levels that were 65 or 10%, respectively, of the 28 degreesC control. Ribulose-1,5-bisphosphate (RuBP) levels increased in heat-stressed leaves, whereas the 3-phosphoglyceric acid pool was depleted. Heat stress did not affect Rubisco per se, as full activity could be restored by incubation with CO2 and Mg2+. Inhibition and recovery of Rubisco activation state and carbon dioxide exchange rate (CER) were closely related under moderate heat stress (up to 42.5 degreesC). Moderate heat stress had negligible effect on Fv/Fm, the maximal quantum yield of photosystem II. In contrast, severe heat stress (45 degreesC) caused significant and irreversible damage to Rubisco activation, CER, and Fv/Fm. The rate of Rubisco activation after alleviating moderate beat stress was comparable to that of controls, indicating rapid reversibility of the process. However, moderate heat stress decreased both the rate and final extent of CER activation during dark-to-light transition. Treatment of cotton leaves with methyl viologen or an oxygen-enriched atmosphere reduced the effect of heat stress on Rubisco inactivation. Both treatments also reduced tissue RuBP levels, indicating that the amount of RuBP present during heat stress may influence the degree of Rubisco inactivation. Under both photorespiratory and non-photorespiratory conditions, the inhibition of the CER during heat stress could be completely reversed by increasing the internal partial pressure of CO2 (Ci). However, the inhibition of the CER by nigericin, a K+ ionophore, was not reversible when the Ci was increased at ambient or high temperature. Our results indicate that inhibition of photosynthesis by moderate heat stress is not caused by inhibition of the capacity for RuBP regeneration. We conclude that heat stress inhibits Rubisco activation via a rapid and direct effect on Rubisco activase, possibly by perturbing Rubisco activase subunit interactions with each other or with Rubisco. [References: 32] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Crafts-Brandner SJ USDA ARS, Western Cotton Res Lab 4135 E Broadway Rd Phoenix, AZ 85040 USA USDA ARS, Western Cotton Res Lab Phoenix, AZ 85040 USA 7 UI - 385KD-0012 AU - Wilson KE AU - Huner NPA TI - The role of growth rate, redox-state of the plastoquinone pool and the trans-thylakoid Delta pH in photoacclimation of Chlorella vulgaris to growth irradiance and temperature SO - Planta 2000 Dec;212(1):93-102 IS - 0032-0935 MH - Chlorella MH - Light-harvesting protein MH - Photoacclimation MH - Temperature MH - Xanthophyll cycle pigment MH - Ii excitation pressure MH - Chlorophyll fluorescence MH - Xanthophyll cycle MH - Winter-wheat MH - Light-intensity MH - Photosystem-ii MH - Dunaliella-tertiolecta MH - Limited photosynthesis MH - Marine-phytoplankton MH - Energy-dissipation AB - The long-term photoacclimation of Chlorella vulgaris Beijer (UTEX 265) to growth irradiance and growth temperature under ambient CO2 conditions was examined. While cultures grew at a faster rate at 27 than at 5 degreesC, growth rates appeared to be independent of irradiance. Decreases in light-harvesting polypeptide accumulation, increases in xanthophyll pool size and changes in the epoxidation state of the xanthophyll cycle pigments were correlated linearly with increases in the relative reduction state of QA, the primary quinone receptor of photosystem II, when estimated as 1-qp under steady-state growth conditions. However, we show that there is also a specific temperature-dependent component, in addition to the redox-state of the QA, involved in regulating the content and composition of light-harvesting complex II of C. vulgaris. In contrast, modulation of the epoxidation state of the xanthophyll pool in response to increased 1-qp in cells grown at 5 OC was indistinguishable from that of cells grown at 27 degreesC, indicating that light and temperature interact in a similar way to regulate xanthophyll cycle activity in C. vulgaris. Because C. vulgaris exhibited a low-light phenotype in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), but a high-light phenotype upon addition of 2,5-dibromo-6-isopropyl-3-methyl-1,4-benzoquinone, we conclude that the plastoquinone pool acts as a sensor regulating the accumulation of light-harvesting polypeptides in C. vulgaris. However, concomitant measurements of non-photochemical fluorescence quenching (q(N)) and the epoxidation state of the xanthophyll pool appear to indicate that, in addition to the redox-state of the plastoquinone pool, the trans-thylakoid Delta pH may also contribute to sensing changes in irradiance and temperature that would lead to over-excitation of the photosynthetic apparatus. We suggest that sink capacity as reflected in photosynthate utilization and cell growth ultimately regulate photoacclimation in C. vulgaris. [References: 46] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Huner NPA Univ Western Ontario, Dept Plant Sci London ON N6A 5B7 Canada Univ Western Ontario, Dept Plant Sci London ON N6A 5B7 Canada 8 UI - 385BV-0032 AU - Franck F AU - Sperling U AU - Frick G AU - Pochert B AU - van Cleve B AU - Apel K AU - Armstrong GA TI - Regulation of etioplast pigment-protein complexes, inner membrane architecture, and protochlorophyllide alpha chemical heterogeneity by light-dependent NADPH : protochlorophyllide oxidoreductases A and B SO - Plant Physiology 2000 Dec;124(4):1678-1696 IS - 0032-0889 MH - 77-k fluorescence emission MH - Dark-grown leaves MH - Hordeum-vulgare-l MH - Chloroplast biogenesis MH - Higher-plants MH - Divinyl protochlorophyllide MH - Chlorophyll biosynthesis MH - Arabidopsis-thaliana MH - Excitation-spectra MH - Etiolated tissues AB - The etioplast of dark-grown angiosperms is characterized by the prolamellar body (PLB) inner membrane, the absence of chlorophyll, and the accumulation of divinyl and monovinyl derivatives of protochlorophyll(ide) a [Pchl(ide) a]. Either of two structurally related, but differentially expressed Light-dependent NADPH:Pchlide oxidoreductases (PORs), PORA and PORE, can assemble the PLB and form dark-stable ternary complexes containing enzymatically photoactive Pchlide-F655. Here we have examined in detail whether these polypeptides play redundant roles in etioplast differentiation by manipulating the total FOR content and the PORA-to-PORB ratio of etiolated Arabidopsis seedlings using antisense and overexpression approaches. FOR content correlates closely with PLB formation, the amounts, spectroscopic properties, and photoreduction kinetics of photoactive Pchlide, the ratio of photoactive Pchlide-F655 to non-photoactive Pchl(ide)-F632, and the ratio of divinyl- to monovinyl-Pchl(ide). This last result defines FOR as the first endogenous protein factor demonstrated to influence the chemical heterogeneity of Pchl(ide) in angiosperms. It is intriguing that excitation energy transfer between different spectroscopic forms of Pchl(ide) in etiolated cotyledons remains largely independent of FOR content. We therefore propose that the PLB contains a minimal structural unit with defined pigment stoichiometries, within which a small amount of non-photoactive Pchl(ide) transfers excitation energy to a large excess of photoactive Pchlide-F655. In addition, our data suggests that FOR may bind not only stoichiometric amounts of photoactive Pchlide, but also substoichiometric amounts of non-photoactive Pchl(ide). We conclude that the typical characteristics of etioplasts are closely related to total FOR content, but not obviously to the specific presence of PORA. or PORE. [References: 59] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Armstrong GA Swiss Fed Inst Technol, Inst Plant Sci Zurich Switzerland Swiss Fed Inst Technol, Inst Plant Sci Zurich Switzerland Univ Liege, Dept Plant Biol, Lab Photobiol Liege Belgium 9 UI - 385BV-0033 AU - Routaboul JM AU - Fischer SF AU - Browse J TI - Trienoic fatty acids are required to maintain chloroplast function at low temperatures SO - Plant Physiology 2000 Dec;124(4):1697-1705 IS - 0032-0889 MH - Acyl-lipid desaturases MH - Chlorophyll fluorescence MH - Arabidopsis mutant MH - Photosynthesis MH - Deficient MH - Leaves MH - Yield AB - The chloroplast membranes of all higher plants contain very high proportions of trienoic fatty acids. To investigate how these lipid structures are important in photosynthesis, we have generated a triple mutant line of Arabidopsis that contains negligible levels of trienoic fatty acids. For mutant plants grown at 22 degreesC, photosynthetic fluorescence parameters were indistinguishable from wild type at 25 degreesC. Lowering the measurement temperature led to a small decrease in photosynthetic quantum yield, Phi (II), in the mutant relative to wild-type controls. These and other results indicate that low temperature has only a small effect on photosynthesis in the short term. However, long-term growth of plants at 4 degreesC resulted in decreases in fluorescence parameters, chlorophyll content, and thylakoid membrane content in triple-mutant plants relative to wild type. Comparisons among different mutant lines indicated that these detrimental effects of growth at 4 degreesC are strongly correlated with trienoic fatty acid content with levels of 16:3 + 18:3, approximately one-third of wild type being sufficient to sustain normal photosynthetic function. In total, our results indicate that trienoic fatty acids are important to ensure the correct biogenesis and maintenance of chloroplasts during growth of plants at low temperatures. [References: 21] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Browse J Washington State Univ, Inst Biol Chem Pullman, WA 99164 USA Washington State Univ, Inst Biol Chem Pullman, WA 99164 USA 10 UI - 385BD-0007 AU - Takechi K AU - Sodmergen AU - Murata M AU - Motoyoshi F AU - Sakamoto W TI - The YELLOW VARIEGATED (VAR2) locus encodes a homologue of FtsH, an ATP-dependent protease in Arabidopsis SO - Plant & Cell Physiology 2000 Dec;41(12):1334-1346 IS - 0032-0781 MH - Arabidopsis thaliana MH - Ftsh MH - Plastid MH - T-dna tagging MH - Variegated mutant MH - Escherichia-coli MH - Chlamydomonas-reinhardtii MH - Gene-expression MH - Photosystem-ii MH - Chloroplast biogenesis MH - Molecular-cloning MH - Inner membrane MH - Higher-plants MH - Cell-growth MH - Degradation AB - Variegated leaves are often caused by a nuclear recessive mutation in higher plants. Characterization of the gene responsible for variegation has shown to provide several pathways involved in plastid differentiation. sere we describe an Arabidopsis variegated mutant isolated by T-DNA tagging, The mutant displayed green and yellow sectors in all green tissues except for cotyledons, Cells in the yellow sector of the mutant contained both normal-appearing and mutant chloroplasts. The isolated mutant was shown to be an allele of the previously reported mutant, yellow variegated (var2), Cloning and molecular characterization of the VAR2 locus revealed that it potentially encodes a chloroplastic homologue of FtsH, an ATP-dependent metalloprotease that belongs to a large protein family involved in various cellular functions. ftsH-like genes appear to comprise a small gene family in Arabidopsis genome, since at least six homologues were found in addition to VAR2. Dispensability of VAR2 was therefore explained by the redundancy of genes coding for FstHs. In the yellow regions of the mutant leaves, accumulation of photosynthetic protein components in the thylakoid membrane appeared to be impaired. Based on the role of FtsH in a protein degradation pathway in plastids, we propose a possibility that VAR2 is required for plastid differentiation by avoiding partial photooxidation of developing chloroplasts. [References: 55] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Sakamoto W Okayama Univ, Bioresources Res Inst 2-20-1 Chuo Okayama 7100046 Japan Okayama Univ, Bioresources Res Inst Okayama 7100046 Japan Peking Univ, Coll Life Sci Beijing 100871 Peoples R China 11 UI - 385BD-0008 AU - Qian P AU - Yagura T AU - Koyama Y AU - Cogdell RJ TI - Isolation and purification of the reaction center (RC) and the core (RC-LH1) complex from Rhodobium marinum: the LH1 ring of the detergent-solubilized core complex contains 32 bacteriochlorophylls SO - Plant & Cell Physiology 2000 Dec;41(12):1347-1353 IS - 0032-0781 MH - Lh1 antenna complex MH - Number of alpha beta subunits MH - Reaction center MH - Reaction center-lh1 core complex MH - Rhodobium marinum MH - Light-harvesting complex MH - Rhodobacter-sphaeroides MH - Rhodopseudomonas-marina MH - Photosynthetic bacteria MH - Purple bacterium MH - Crystal-structure MH - Protein subunits MH - Antenna MH - Unit MH - B820-subunit AB - The reaction center (RC) and the core (RC-LH1) complex were isolated and purified from Rhodobium marinum; together with the LH1 complex [Meckenstock et al. (1992a) FEES Lett, 311: 128], a complete set of RC, LH1 and RC-LH1 from the same wild-type strain of a purple photosynthetic bacterium can therefore now be made. Comparison of the BChl a/BPhe a ratio (determined by HPLC) between the RC and the RC-LH1 complexes lead us to the determination of the number of BChls in the LH1 ring to be 32.06 +/- 2.90, indicating that the LH1 ring from Rh. marinum consists of 16 alpha beta subunits. [References: 28] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Koyama Y Kwansei Gakuin Univ, Fac Sci Nishinomiya Hyogo 6628501 Japan Kwansei Gakuin Univ, Fac Sci Nishinomiya Hyogo 6628501 Japan Univ Glasgow, Inst Biochem & Life Sci, Div Biochem & Mol Biol Glasgow G12 8QQ Lanark Scotland 12 UI - 385BD-0009 AU - Enami I AU - Yoshihara S AU - Tohri A AU - Okumura A AU - Ohta H AU - Shen JR TI - Cross-reconstitution of various extrinsic proteins and photosystem II complexes from cyanobacteria, red algae and higher plants SO - Plant & Cell Physiology 2000 Dec;41(12):1354-1364 IS - 0032-0781 MH - Evolution MH - Extrinsic proteins MH - Oxygen evolution MH - Photosynthesis MH - Photosystem ii MH - Reconstitution MH - Photosynthetic oxygen-evolution MH - Synechocystis sp pcc-6803 MH - Cytochrome c-550 MH - Synechococcus-vulcanus MH - Functional-properties MH - Cyanidium-caldarium MH - 33-kda protein MH - 12-kda protein MH - Kda protein MH - Binding AB - Photosystem II (PSII) contains different extrinsic proteins required for oxygen evolution among different organisms, Cyanobacterial PSII contains the 33 kDa, 12 kDa proteins and cytochrome (cyt) c-550; red algal PSII contains a 20 kDa protein in addition to the three homologous cyanobacterial proteins; whereas higher plant PSII contains the 33 kDa, 23 kDa and 17 kDa proteins, In order to understand the binding and functional properties of these proteins, we performed cross-reconstitution experiments with combinations of PSII and extrinsic proteins from three different sources: higher plant (spinach), red alga (Cyanidium caldarium) and cyanobacterium (Synechococcus vulcanus). among all of the extrinsic proteins, the 33 kDa protein is common to all of the organisms and is totally exchangeable in binding to PSII from any of the three organisms, Oxygen evolution of higher plant and red algal PSII was restored to a more or less similar level by binding of any one of the three 33 kDa proteins, whereas oxygen evolution of cyanobacterial PSII was restored to a larger extent with its own 33 kDa protein than with the 33 kDa protein from other sources, In addition to the 33 kDa protein, the red algal 20 kDa, 12 kDa proteins and cyt c-550 were able to bind to cyanobacterial and higher plant PSII, leading to a partial restoration of oxygen evolution in both organisms, The cyanobacterial 12 kDa protein and cyt c-550 partially bound to the red algal PSII, but this binding did not restore oxygen evolution, The higher plant 23 kDa and 17 kDa proteins bound to the cyanobacterial and red algal PSII only through non-specific interactions, Thus, only the red algal extrinsic proteins are partially functional in both the cyanobacterial and higher plant PSII, which implies a possible intermediate position of the red algal PSII during its evolution from cyanobacteria to higher plants. [References: 19] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Enami I Sci Univ Tokyo, Fac Sci, Dept Biol, Shinjuku Ku Kagurazaka 1-3 Tokyo 1628601 Japan Sci Univ Tokyo, Fac Sci, Dept Biol, Shinjuku Ku Tokyo 1628601 Japan RIKEN, Harima Inst Mikazuki Hyogo 6795148 Japan 13 UI - 385BD-0014 AU - Yamaguchi K AU - Nishimura M TI - Reduction to below threshold levels of glycolate oxidase activities in transgenic tobacco enhances photoinhibition during irradiation SO - Plant & Cell Physiology 2000 Dec;41(12):1397-1406 IS - 0032-0781 MH - Calvin cycle MH - Glycolate oxidase MH - Glycolate pathway MH - Hydroxypyruvate reductase MH - Photoinhibition MH - Photorespiration MH - Dependent hydroxypyruvate reductase MH - Pumpkin cotyledons MH - Chlorophyll fluorescence MH - Glycine decarboxylase MH - Nitrate reductase MH - Leaf peroxisomes MH - Arabidopsis MH - Expression MH - Gene MH - Cucumber AB - The effects of decreased flux in the glycolate pathway on photoinhibition was investigated in transgenic tobacco (Nicotiana tabacum L. cv. SR1) plants. These plants harbored a pumpkin cDNA for glycolate oxidase (GO), an enzyme in the glycolate pathway, under the control of the cauliflower mosaic virus 35S promoter, Some transformants showed both reduced amounts and reduced activities of GO. The decrease of GO was enhanced at a later growth stage of these transformants, whereas no changes were observed in the amounts of other enzymes in the glycolate pathway, such as hydroxypyruvate reductase and serine glyoxylate aminotransferase. The phenotype grown under a low light condition (30 muE s(-1) m(-2)) resembled that of the wild type. Transformants with about 35% lower GO activity than wild type, had a lower Fv/Fm under 500 muE S-1 m(-2) irradiation for 8 h. After 60 muE s(-1) m(-2) irradiation for 8 h, Fv/Fm was lowered in some transformants with less than 20% of the GO activity of the wild type. These results suggest that photosynthesis was susceptible to photoinhibition with reduction to below threshold levels of GO activities and that higher activities of GO are required under a higher irradiation. The increase in the electron transport rate (ETR) with increased irradiation was suppressed only in transformants that had GO activity one-third less than the wild type, suggesting that the regeneration of the substrate for the Calvin cycle was decreased only when there was an extreme reduction of GO. These results also suggest that the photosystem was disturbed when the concentration of the substrate for the Calvin cycle decreased until it became insufficient to receive the excess photon energy generated in each light environment. [References: 47] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Nishimura M Natl Inst Basic Biol, Dept Cell Biol Okazaki Aichi 4448585 Japan Natl Inst Basic Biol, Dept Cell Biol Okazaki Aichi 4448585 Japan 14 UI - 385WF-0008 AU - Ivanov AG AU - Miskiewicz E AU - Clarke AK AU - Greenberg BM AU - Huner NPA TI - Protection of photosystem II against UV-A and UV-B radiation in the cyanobacterium Plectonema boryanum: The role of growth temperature and growth irradiance SO - Photochemistry & Photobiology 2000 Dec;72(6):772-779 IS - 0031-8655 MH - Nostoc commune MH - Light MH - Synechococcus MH - Pigment MH - Carotenoids MH - Acclimation AB - Plectonema boryanum UTEX 485 cells were grown at 29 degreesC and 150 mu mol m(-2) s(-1) photosynthetically active radiation (PAR) and exposed to PAR combined with ultraviolet-A radiation (UV-A) at 15 degreesC. This induced a time-dependent inhibition of photosystem II (PSII) photochemistry measured as a decrease of the chlorophyll a fluorescence ratio, F-v/F-m to 50% after 2 h of W-A treatment compared to nontreated control cells. Exposure of the same cells to PAR combined with W-A + ultraviolet-B radiation (UV-B) caused only a 30% inhibition of PSII photochemistry relative to nontreated cells. In contrast, UV-A and UV-A + UV-B irradiation of cells cultured at 15 degreesC and 150 mu mol m(-2) s(-1) had minimal effects on the F-v/F-m values. However, cells grown at 15 degreesC and lower PAR irradiance (6 mu mol m(-2) s(-1)) exhibited similar inhibition patterns of PSII photochemistry as control cells. The decreased sensitivity of PSII photochemistry of P. boryanum grown at 15 degreesC and 150 mu mol m(-2) s(-1) to subsequent exposure to UV radiation relative to either control cells or cells grown at low temperature but low irradiance was correlated with the following: (1) a reduced efficiency of energy transfer to PSII reaction centers; (2) higher levels of a carotenoid tentatively identified as myxoxanthophyll; (3) the accumulation of scytonemin and mycosporine amino acids; and (4) the accumulation of ATP-dependent caseinolytic proteases. Thus, acclimation of P, boryanum at low temperature and moderate irradiance appears to confer significant resistance to UV-induced photoinhibition of PSII. The role of excitation pressure in the induction of this resistance to UV radiation is discussed. [References: 32] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Huner NPA Univ Western Ontario, Dept Plant Sci 1151 Richmond St N London ON N6A 5B7 Canada Univ Western Ontario, Dept Plant Sci London ON N6A 5B7 Canada Bulgarian Acad Sci, Inst Biophys Sofia Bulgaria Umea Univ, Dept Plant Physiol S-90187 Umea Sweden Univ Waterloo, Dept Biol Waterloo ON N2L 3G1 Canada 15 UI - 384QU-0036 AU - Chen RF AU - Jiang Y AU - Zhao M TI - Solid-phase fluorescence determination of chlorins in marine sediments SO - Organic Geochemistry 2000;31(12):1755-1763 IS - 0146-6380 MH - Chlorins MH - Paleoproductivity MH - Fluorescence MH - Analysis MH - Non-destructive MH - Laser-induced fluorescence MH - Organic-matter MH - Reflectance spectroscopy MH - Chlorophyll MH - Paleoproductivity MH - Atlantic MH - Ocean MH - Proxy MH - Productivity MH - Preservation AB - Chlorophyll degradation products are preserved in marine sediments over timescales of thousands of years. The production of chlorophyll in the water column is related to biological productivity, so chlorophyll degradation products (chlorins) preserved in marina sediments can be used as indicators of paleoproductivity. A new, rapid, nondestructive method of determining chlorin concentrations in marine sediments is presented. Potential interferences associated with the solid-phase fluorescence (SPF) method are explored using reference materials, yet this method compares favorably with spectroscopic and high performance liquid chromatographic (HPLC) methods of analysis using marine sediments from Boston Harbor and the continental shelf off northwest Africa. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 46] LG - English PT - Article SB - Current Contents(R)/Physical, Chemical & Earth Sciences IN - Chen RF Univ Massachusetts 100 Morrissey Blvd Boston, MA 02125 USA Univ Massachusetts Boston, MA 02125 USA Dartmouth Coll, Dept Earth Sci Hanover, NH 03755 USA 16 UI - 384QF-0009 AU - von Felten P AU - Bachofen R TI - Continuous monitoring of the cytoplasmic pH in Methanobacterium thermoautotrophicum using the intracellular factor F-420 as indicator SO - Microbiology 2000 Dec;146(Part 12):3245-3250 IS - 1350-0872 MH - Cytoplasm MH - Ph gradient MH - Intracellular ph MH - Protonmotive force MH - Methanogenic bacteria MH - Methanococcus-voltae MH - Cells MH - Bacteria MH - Membrane MH - Cultures MH - Archaea MH - Growth MH - Probe AB - The absorption spectrum of factor F-420 changes depending on the pH and the redox state of the cytoplasm. Specific wavelengths were used to calibrate absorption changes to allow the measurement of changes in the cytoplasmic ph in Methanobacterium thermoautotrophicum. Upon a hydrogen pulse, a rapid efflux of protons was observed. Under these energized conditions, the Delta pH amounts to 0.2-0.4 pH units at ph 6.6, and 0.6-0.8 pH units at pH 6.0. It decays within 10-20 s. In parallel, a sodium gradient is formed which has a slightly longer lifetime. Both Delta pH and Delta Psi contribute to the proton-motive force present during methanogenesis. The energy-conversion rate, as indicated by the decay of the energized state of the cell, is fastest under growth conditions, i.e. at ph 6.9 and at a temperature of 58 degreesC. [References: 26] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Bachofen R Univ Zurich, Inst Plant Biol Zollikerstr 107 CH-8008 Zurich Switzerland Univ Zurich, Inst Plant Biol CH-8008 Zurich Switzerland 17 UI - 385HF-0004 AU - Downs CA AU - Mueller E AU - Phillips S AU - Fauth JE AU - Woodley CM TI - A molecular biomarker system for assessing the health of coral (Montastraea faveolata) during heat stress SO - Marine Biotechnology 2000 Nov-Dec;2(6):533-544 IS - 1436-2228 MH - Coral reefs MH - Heat stress MH - Molecular biomarkers MH - Nadh-ubiquinone oxidoreductase MH - Shock-protein MH - Oxidative stress MH - Photosystem-ii MH - Elevated-temperatures MH - Ultraviolet-radiation MH - Scleractinian corals MH - Endosymbiotic algae MH - Electron-transport MH - Zooxanthellae AB - Using a novel molecular biomaker system (MBS), we assessed the physiological status of coral (Montastraea faveolata) challenged by heat stress by assaying specific cellular and molecular parameters. This technology is particularly relevant for corals because heat stress is thought to be an essential component of coral bleaching. This phenomenon is widely believed to be responsible for coral mortality worldwide, particularly during 1997-1998. Specific parameters of coral cellular physiology were assayed using the MBS that are indicative of a nonstressed or stressed condition. The MBS distinguished the separate and combined effects of heat and light on the 2 coral symbionts, a sclerctinian coral and a dinoflagellate algae (zooxanthellae). This technology aids in the accurate diagnosis of coral condition because each parameter is physiologically well understood. Finally, the MBS technology is relatively inexpensive, easy to implement, and precise, and it can be quickly adapted to a high-throughout robotic system for mass sample analysis. [References: 62] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences IN - Downs CA Envirtue Biotechnol Inc 1361 Yosernite Circle Clayton, CA 94517 USA Envirtue Biotechnol Inc Clayton, CA 94517 USA NOAA, Marine Biotechnol Program, Natl Ocean Serv, Ctr Coastal Environm Hlth & Biomol Res Charleston, SC 29412 USA Mote Marine Lab, Ctr Trop Res Summerland Key, FL 33042 USA Brevard Community Coll, Dept Sci Biol Palm Bay, FL 32909 USA Univ Charleston, Dept Biol Charleston, SC 29422 USA 18 UI - 385LK-0002 AU - Rijstenbil JW AU - Coelho SM AU - Eijsackers M TI - A method for the assessment of light-induced oxidative stress in embryos of fucoid algae via confocal laserscan microscopy SO - Marine Biology 2000 Dec;137(5-6):763-774 IS - 0025-3162 MH - Ultraviolet-b radiation MH - Free-radical production MH - Chlorella-vulgaris MH - Oxygen production MH - Uv-b MH - Chlorophyll fluorescence MH - Hydroxyl radicals MH - Active oxygen MH - Photoinhibition MH - Plants AB - A method was developed for measurement of active oxygen production in embryonic stages of the brown seaweed Fucus spiralis. using the label CM-DCFH-DA. Active oxygen species convert the label into the green fluorescent CM-DCF (exc/em 488/530 nm) that is detected via confocal laserscan microscopy and quantitative image analysis. Loading of the label did not harm the embryos; loading efficiency was age-independent, and the esterases needed for conversion to CM-DCFH were not inhibited by the effective UV dose (2 W m(-2)) applied in the experiments. After correction for daily valiation of the laser power, and calibration with DCF standard solutions, this automated analysis of confocal images rendered active oxygen concentrations in fucoid embryos (muM DCF). An experiment was designed for the assessment of active oxygen production following irradiance stress in the light-sensitive embryos. Dim-light-acclimated, 1-, 2- and 3-day-old embryos were transferred for 60 min to conditions (4 pi -irradiance 300 mu mol photons m(-2) s(-1)), optionally without UV radiation, including UVA, or including UVA plus UVB. PSII yield measurements (PAM fluorometer) were carried out in order to assess the degree of photoinhibition under these light conditions. The imposed light stress initially caused a rapid decrease of the PSII yields (Phi (P)). With increasing embryo age, minimum Phi (P) values attained under light stress remained higher. Consequently, electron transport rates (ETR) would increase with embryo age, i.e., with the development of their photosynthetic apparatus. Active oxygen production increased with ETR, and when WE was included, relatively greater amounts of active oxygen were produced. A slow, second-phase decrease of Phi (P) under light stress that was proportional to active oxygen production indicated that some photooxidative damage was caused, in particular during UVB exposure. Recovery from light stress was a rapid process in the absence of UVB; in such cases Phi (P) was almost restored to the initial values within 60 min. The relative state of recovery of Phi (P) was correlated with both the effective UV dose and active oxygen production rate (DCF). Recovery was slowest in embryos exposed for 60 min to an experimental UVB dose, which was representative of a situation at low tide, on a sunny day. The results suggest that active oxygen may cause an in situ inhibition of growth of the earliest life stages of F. spiralis. [References: 40] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences IN - Rijstenbil JW Netherlands Inst Ecol, Ctr Estaurine & Coastal Res, NIOO, CEMO POB 140 NL-4400 AC Yerseke Netherlands Netherlands Inst Ecol, Ctr Estaurine & Coastal Res, NIOO, CEMO NL-4400 AC Yerseke Netherlands Leica Microsyst Wetzlar GmbH D-35578 Wetzlar Germany 19 UI - 385PG-0019 AU - Katz E AU - Deehan MR AU - Seatter S AU - Lord C AU - Sturrock RD AU - Harnett MM TI - B cell receptor-stimulated mitochondrial phospholipase A(2) activation and resultant disruption of mitochondrial membrane potential correlate with the induction of apoptosis in WEHI-231 B cells SO - Journal of Immunology 2001 Jan 1;166(1):137-147 IS - 0022-1767 MH - Fas-mediated apoptosis MH - Cytochrome-c MH - Permeability transition MH - Caspase activation MH - Antigen receptors MH - Lymphoma-cells MH - Death MH - Bcl-x(l) MH - Bcl-2 MH - Lymphocytes AB - Cross-linking of the Ag receptors on the immature B cell lymphoma, WEHI-231, leads to growth arrest and apoptosis, We now show that although commitment to such B cell receptor (BCR)-mediated apoptosis correlates with mitochondrial phospholipase A(2) activation, disruption of mitochondrial function, and ATP depletion, it is executed independently of caspase activation. First, we demonstrate a pivotal role for mitochondrial function in determining B cell fate by showing up-regulation of cytosolic phospholipase A(2) expression, induction of mitochondrial phospholipase A, activity, arachidonic acid-mediated collapse of mitochondrial transmembrane inner potential (Delta psi (m)), and depletion of cellular ATP under conditions of apoptotic, but not proliferative, signaling via the BCR. Importantly, disruption of Delta psi (m), ATP depletion, and apoptosis can be prevented by rescue signals via CD40 or by Delta psi (m) stabilizers such as antimycin or oligomycin. Second, we show that commitment and postmitochondrial execution of BCR-mediated apoptosis are not dependent on caspase activation by demonstrating that such apoptotic signaling does not induce release of cytochrome c from the mitochondria or activation of effector caspases, as evidenced by poly(ADP-ribose) polymerase or Bcl-x(L) cleavage. Indeed, apoptotic signaling via the BCR in WEHI-231 B cells does not stimulate the activation of caspase-3 and, consistent with this, BCR-mediated disruption of Delta psi (m) and commitment to apoptosis take place in the presence of caspase inhibitors. In contrast, BCR signaling induces the postmitochondrial activation of cathepsin B, and resultant apoptosis is blocked by the cathepsin B inhibitor, (23,35)trans-epoxysuccinyl-L-leucylamindo-3-methylbutane ethyl ester (EST) suggesting a key role for this executioner protease in Ag receptor-driven apoptosis of WEHI-231 immature B cells. [References: 65] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Harnett MM Univ Glasgow, Western Infirm, Dept Immunol Dumbarton Rd Glasgow G11 6NT Lanark Scotland Univ Glasgow, Dept Immunol Glasgow Lanark Scotland Royal Infirm, Ctr Rheumat Dis Glasgow G31 2ER Lanark Scotland 20 UI - 385BN-0012 AU - Allen DJ AU - Ratner K AU - Giller YE AU - Gussakovsky EE AU - Shahak Y AU - Ort DR TI - An overnight chill induces a delayed inhibition of photosynthesis at midday in mango (Mangifera indica L.) SO - Journal of Experimental Botany 2000 Nov;51(352):1893-1902 IS - 0022-0957 MH - Chilling temperatures MH - Chlorophyll fluorescence MH - Circadian rhythm MH - Leaf gas exchange MH - Stomata MH - Water-stress MH - Stomatal conductance MH - Co2 assimilation MH - Reductive activation MH - Phaseolus-vulgaris MH - Electron-transfer MH - Sensitive plants MH - Rubisco activase MH - Quantum yield MH - Gas-exchange AB - The effect of a cold night on photosynthesis in herbaceous chilling-sensitive crops, like tomato, has been extensively studied and is well characterized. This investigation examined the behaviour of the subtropical fruit tree, mango, to enable comparison with these well-studied systems. Unlike tomato, chilling between 5 degreesC and 7 degreesC overnight produced no significant inhibition of light-saturated CO2 assimilation (A) during the first hours following rewarming, measured either under controlled environment conditions or in the field. By midday, however, there was a substantial decline in A, which could not be attributed to photoinhibition of PSII, but rather was associated with an increase in stomatal limitation of A and lower Rubisco activity. Overnight chilling of tomato can cause severe disruption in the circadian regulation of key photosynthetic enzymes and is considered to be a major factor underlying the dysfunction of photosynthesis in chilling-sensitive herbaceous plants. Examination of the gas exchange of mango leaves maintained under constant conditions for 2 d, demonstrated that large depressions in A during the subjective night were primarily the result of stomatal closure. Chilling did not disrupt the ability of mango leaves to produce a circadian rhythm in stomatal conductance. Rather, the midday increase in stomatal limitation of A appeared to be the result of altered guard cell sensitivity to CO2 following the dark chill. [References: 50] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Ort DR Univ Illinois, USDA ARS, Photosynthesis Res Unit Urbana, IL 61801 USA Univ Illinois, USDA ARS, Photosynthesis Res Unit Urbana, IL 61801 USA Univ Illinois, Dept Plant Biol Urbana, IL 61801 USA Agr Res Org, Volcani Ctr, Inst Hort IL-50250 Bet Dagan Israel 21 UI - 384QH-0008 AU - Bishop T AU - Brand MD TI - Processes contributing to metabolic depression in hepatopancreas cells from the snail Helix aspersa SO - Journal of Experimental Biology 2000 Dec;203(23):3603-3612 IS - 0022-0949 MH - Metabolic depression MH - Helix aspersa MH - Hepatopancreas MH - Isolated cells MH - Non-mitochondrial respiration MH - Mitochondrial respiration MH - Proton leak MH - Aestivation MH - Oxygen conformation MH - Oxyconformation MH - Mollusc MH - Land snail MH - Mitochondrial inner membrane MH - Proton permeability MH - Otala-lactea MH - Liver-mitochondria MH - Hepatocytes MH - Anoxia MH - Oxygen MH - Leak MH - Suppression MH - Respiration AB - Cells isolated from the hepatopancreas of the land snail Helix aspersa strongly depress respiration both immediately in response to lowered PO2 (oxygen conformation) and, in the longer term, during aestivation, These phenomena were analysed by dividing cellular respiration into non-mitochondrial and mitochondrial respiration using the mitochondrial poisons myxothiazol, antimycin and azide, Non-mitochondrial respiration accounted for a surprisingly large proportion, 65+/-5 %, of cellular respiration in control cells at 70 % air saturation. Non-mitochondrial respiration decreased substantially as oxygen tension was lowered, but mitochondrial respiration did not, and the oxygen-conforming behaviour of the cells was due entirely to the oxygen-dependence of nonmitochondrial oxygen consumption. Non-mitochondrial respiration was still responsible for 45+/-2 % of cellular respiration at physiological oxygen tension. Mitochondrial respiration was further subdivided into respiration used to drive ATP turnover and respiration used to drive futile proton cycling across the mitochondrial inner membrane using the ATP synthase inhibitor oligomycin, At physiological oxygen tensions, 34+/-5 % of cellular respiration was used to drive ATP turnover and 22+/-4 % was used to drive proton cycling, echoing the metabolic inefficiency previously observed in liver cells from mammals, reptiles and amphibians. The respiration rate of hepatopancreas cells from aestivating snails was only 37 % of the control value. This was caused by proportional decreases in non-mitochondrial and mitochondrial respiration and in respiration to drive ATP turnover and to drive proton cycling. Thus, the fraction of cellular respiration devoted to different processes remained constant and the cellular energy balance was preserved in the hypometabolic state. [References: 38] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Life Sciences IN - Bishop T MRC, Dunn Human Nutr Unit Hills Rd Cambridge CB2 2XY England MRC, Dunn Human Nutr Unit Cambridge CB2 2XY England 22 UI - 385UQ-0010 AU - Gniadecki R AU - Thorn T AU - Vicanova J AU - Petersen A AU - Wulf HC TI - Role of mitochondria its ultraviolet-induced oxidative stress SO - Journal of Cellular Biochemistry 2000;80(2):216-222 IS - 0730-2312 MH - Free radicals MH - Hydrogen peroxide MH - Respiratory chain MH - Internucleosomal dna fragmentation MH - Programmed cell-death MH - Necrosis-factor-alpha MH - Hydrogen-peroxide MH - Ionizing-radiation MH - Apoptosis MH - Oxygen MH - Activation MH - Generation MH - Metabolism AB - The biological effects of ultraviolet radiation (UV), such as DNA damage, mutagenesis, cellular aging, and carcinogenesis, are in part mediated by reactive oxygen species (ROS). The major intracellular ROS intermediate is hydrogen peroxide, which is synthesized from superoxide anion (O-.(2)-) and further metabolized into the highly reactive hydroxyl radical. In this study, we examined the involvement of mitochondria in the UV-induced H2O2 accumulation in a keratinocyte cell line HaCaT. Respiratory chain blockers (cyanide-p-trifluoromethoxyphenylhydrazone and oligomycin) and the complex II inhibitor (theonyltrifluoroacetone) prevented H2O2 accumulation after UV. Antimycin A that inhibits electron flow from mitochondrial complex III to complex IV increased the UV-induced H2O2 synthesis. The same effect was seen after incubation with rotenone, which blocks electron flow from NADH-reductase (complex I) to ubiquinone. UV irradiation did not affect mitochondrial transmembrane potential (Delta Psi (m)). These data indicate that UV-induced ROS are produced at complex III via complex ii (succinate-Q-reductase).). Cell. Biochem. 80:216-222, 2000. (C) 2000 Wiley-Liss, Inc. [References: 40] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Gniadecki R Bispebjerg Hosp, Dept Dermatol D 92,Bispebjerg Bakke 23 DK-2400 Copenhagen NV Denmark Copenhagen Univ Hosp, Dept Dermatol Copenhagen Denmark 23 UI - 385UQ-0014 AU - Perks CM AU - McCaig C AU - Holly JMP TI - Differential insulin-like growth factor (IGF)-independent interactions of IGF binding protein-3 and IGF binding protein-5 on apoptosis in human breast cancer cells. Involvement of the mitochondria. SO - Journal of Cellular Biochemistry 2000;80(2):248-258 IS - 0730-2312 MH - Apoptosis MH - Mitochondria MH - Insulin-like growth factor-binding proteins MH - Factor binding-protein-3 MH - Ceramide MH - Death MH - Disruption MH - Generation MH - Inhibition MH - Receptor MH - Adhesion AB - We have demonstrated previously in Hs578T cells that insulin-like growth factor binding protein (IGFBP)-3 can significantly accentuate ceramide (C2)-induced apoptosis, but has no effect on cell death induced by integrin detachment [using an arginine-glycine-aspartic acid (RCD)-containing peptide]. In contrast we found that IGFBP-5 could inhibit apoptosis induced by either C2 or integrin detachment. It is now clear that the mitochondria not only provide the energy required for cell viability, but can also play an important role during the commitment phase to apoptosis. We used a mitochondrial respiratory chain inhibitor, antimycin A, at both apoptotic and nonapoptotic doses to further investigate the IGF-independent actions of IGFBP-3 and IGFBP-5 on C2 and RGD-induced apoptosis in the Hs578T cells. Hs578T cells had one of three treatments, 1: They were incubated with increasing doses of antimycin A for 24 h. 2: They were coincubated with an apoptotic dose of either C2 or RGD together with a nonapoptotic dose of antimycin A for 24 h. 3: They were incubated with a binding protein (100 ng/ml) for 24 h followed by coincubation of the binding protein with an apoptotic dose of antimycin A for a further 24 h. Cell viability was assessed by trypan blue dye exclusion and MTT assay, and apoptosis was confirmed and measured by morphologic assessment and flow cytometry. We found that antimycin A initiated apoptosis at 10 mu mol/L and above. We also demonstrated that a nonapoptotic dose of antimycin A (0.1 mu mol/L) significantly inhibited C2-induced apoptosis, whereas it significantly accentuated RGD-induced cell death. In addition, we found that cell death induced by antimycin A can be accentuated by IGFBP-3 but is not affected by IGFBP-5. These data indicate that IGFBP-3 can directly enhance apoptosis triggered via the mitochondria; either directly by a mitochondrial inhibitor or by C2 (which we demonstrate to act via effects on the mitochondria in this model). IGFBP-5, however, appears to confer survival effects via a distinct pathway not involving the mitochondria. J. Cell. Biochem. 80.248-258, 2000. (C) 2000 Wiley-Liss, Inc. [References: 36] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Perks CM Bristol Royal Infirm, Dept Hosp Med, Div Surg Bristol BS2 8HW Avon England Bristol Royal Infirm, Dept Hosp Med, Div Surg Bristol BS2 8HW Avon England 24 UI - 384PB-0027 AU - Thorsteinsson MV AU - Kerby RL AU - Conrad M AU - Youn H AU - Staples CR AU - Lanzilotta WN AU - Poulos TJ AU - Serate J AU - Roberts GP TI - Characterization of variants altered at the N-terminal proline, a novel heme-axial ligand in CooA, the CO-sensing transcriptional activator SO - Journal of Biological Chemistry 2000 Dec 15;275(50):39332-39338 IS - 0021-9258 MH - Magnetic circular-dichroism MH - Site-directed mutagenesis MH - Soluble guanylate-cyclase MH - Carbon-monoxide MH - Rhodospirillum-rubrum MH - Nitric-oxide MH - Receptor protein MH - Fluorescence polarization MH - Myoglobin MH - Ligation AB - Cook the carbon monoxide-sensing transcription factor from Rhodospirillum rubrum, binds CO through a heme moiety resulting in conformational changes that promote DNA binding. The crystal structure shows that the N-terminal Pro(2) Of one subunit (Met(1) is removed post-translationally provides one ligand to the heme of the other subunit in the Cook homodimer. To determine the importance of this novel ligand and the contiguous residues to Cook function, we have altered the N terminus through two approaches: site directed mutagenesis and regional randomization, and characterized the resulting Cook variants. While Pro(2) appears to be optimal for Cook function, it is not essential and a variety of studied variants at this position have substantial CO-sensing function. Surprisingly, even alterations that add a residue (where Pro(2) is replaced by Met(1)-Tyr(2), for example) accumulate heme-containing Cook with functional properties that are similar to those of wild-type Cook Other nearby residues, such as Phe(5) and Asn(6) appear to be important for either the structural integrity or the function of Cook These results are contrasted with those previously reported for alteration of the His(77) ligand on the opposite side of the heme. [References: 45] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Roberts GP Univ Wisconsin, Dept Bacteriol Madison, WI 53706 USA Univ Wisconsin, Dept Bacteriol Madison, WI 53706 USA Univ Wisconsin, Dept Biochem Madison, WI 53706 USA Univ Calif Irvine, Dept Biochem & Mol Biol Irvine, CA 92697 USA 25 UI - 384PB-0048 AU - Lancaster CRD AU - Bibikova MV AU - Sabatino P AU - Oesterhelt D AU - Michel H TI - Structural basis of the drastically increased initial electron transfer rate in the reaction center from a Rhodopseudomonas viridis mutant described at 2.00-angstrom resolution SO - Journal of Biological Chemistry 2000 Dec 15;275(50):39364-39368 IS - 0021-9258 MH - Photosynthetic reaction-center MH - Membrane-protein complex MH - Crystal-structures MH - Purple bacteria MH - Photosystem-ii MH - Rhodobacter-sphaeroides MH - Functional implications MH - Charge separation MH - 3a resolution MH - Density maps AB - It has previously been shown that replacement of the residue His L168 with Phe (HL168F) in the Rhodopseudomonas viridis reaction center (RC) leads to an unprecedented drastic acceleration of the initial electron transfer rate. Here we describe the determination of the x-ray crystal structure at 2.00-Angstrom resolution of the HL168F RC. The electron density maps confirm that a hydrogen bond from the protein to the special pair is removed by this mutation. Compared with the wild-type RC, the acceptor of this hydrogen bond, the ring I acetyl group of the "special pair" bacteriochlorophyll, D-L, is rotated, and its acetyl oxygen is found 1.1 Angstrom closer to the bacteriochlorophyll-Mg2+ Of the other special pair bacteriochlorophyll, D-M. The rotation of this acetyl group and the increased interaction between the D-L ring I acetyl oxygen and the D-M-Mg2+ provide the structural basis for the previously observed 80-mV decrease in the D+/D redox potential and the drastically increased rate of initial electron transfer to the accessory bacteriochlorophyll, B-A The high quality of the electron density maps also allowed a reliable discussion of the mode of binding of the triazine herbicide terbutryn at the binding site of the secondary quinone, Q(B). [References: 55] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Lancaster CRD Max Planck Inst Biophys, Abt Mol Membranbiol Heinrich Hoffmann Str 7 D-60528 Frankfurt Germany Max Planck Inst Biophys, Abt Mol Membranbiol D-60528 Frankfurt Germany Max Planck Inst Biochem, Abt Membranbiochem D-82152 Martinsried Germany 26 UI - 383RW-0001 AU - Montane MH AU - Kloppstech K TI - The family of light-harvesting-related proteins (LHCs, ELIPs, HLIPs): was the harvesting of light their primary function? [Review] SO - Gene 2000 Nov 27;258(1-2):1-8 IS - 0378-1119 MH - Light harvesting antennae MH - Light stress complexes MH - Elip MH - Hlip MH - Lhc proteins MH - Evolution MH - Induced stress proteins MH - A/b-binding-proteins MH - Plant photosystem-ii MH - 22 kda protein MH - Complex MH - Acclimation MH - Gene MH - Photoinhibition MH - Cyanobacteria MH - Subunit AB - Light-harvesting complex proteins (LHCs) and early light-induced proteins (ELIPs) are essential pigment-binding components of the thylakoid membrane and are encoded by one of the largest and most complex higher plant gene families. The functional diversification of these proteins corresponded to the transition from extrinsic (phycobilisome-based) to intrinsic (LHC-based) light-harvesting antenna systems during the evolution of chloroplasts from cyanobacteria, yet the functional basis of this diversification has been elusive. Here, we propose that the original function of LHCs and ELIPs was not to collect light and to transfer its energy content to the reaction centers but to disperse the absorbed energy of light in the form of heat or fluorescence. These energy-dispersing proteins are believed to have originated in cyanobacteria as one-helix, highly light-inducible proteins (HLIPs) that later acquired four helices through two successive gene duplication steps. We suggest that the ELIPs arose first in this succession, with a primary function in energy dispersion for protection of photosynthetic pigments from photo-oxidation. We consider the LHC I and II families as more recent and very successful evolutionary additions to this family that ultimately attained a new function, thereby replacing the ancestral extrinsic light-harvesting system. Our model accounts for the non-photochemical quenching role recently shown for higher plant psbS proteins. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 43] LG - English PT - Review SB - Current Contents(R)/Life Sciences IN - Kloppstech K Univ Hannover, Inst Bot Herrenhauser Str 2 D-30419 Hannover Germany Univ Hannover, Inst Bot D-30419 Hannover Germany CEA Cadarache, DSV, DEVM, Lab Radiobiol Vegetale F-13108 St Paul Durance France 27 UI - 383RW-0012 AU - Chae JC AU - Kim Y AU - Kim YC AU - Zylstra GJ AU - Kim CK TI - Genetic structure and functional implication of the fcb gene cluster for hydrolytic dechlorination of 4-chlorobenzoate from Pseudomonas sp DJ-12 SO - Gene 2000 Nov 27;258(1-2):109-116 IS - 0378-1119 MH - Dechlorination gene MH - Evolutionary relationship MH - Genetic organization MH - Transporter gene MH - Amino-acid-sequence MH - Rhodobacter-capsulatus MH - Strain cbs-3 MH - Dehalogenase MH - Protein MH - Resolution MH - Database AB - The fcb gene cluster responsible for the hydrolytic dechlorination of 4-chlorobenzoate (4CBA) was cloned from the chromosomal DNA of Pseudomonas sp. DJ-12, and its nucleotide sequence analyzed. The gene cluster was organized in the order fcbB-fcbA-fcbT1-fcbT2-cbT3-fcbC, which is different from that reported in other bacteria. A promoter-like sequence (-35 and -10 region) is located upstream of the fcbB gene and putative ribosome-binding sequences were found upstream of the respective orfs. A stem-loop transcription terminator structure is found downstream of fcbC. This suggests that the six orfs are transcribed into a polycistronic mRNA. The FcbA, FcbB, and FcbC enzymes for dechlorination of 4CBA have a relationship in common with the enzymes involved in fatty acid metabolism on the basis of their deduced amino acid sequences. The proteins encoded by fcbT1, fcbT2, and fcbT3 show similarity to those encoded by dctP, dctQ, and dctM of Rhodobacter capsulatus respectively, which encode transporter proteins for C4-dicarboxylate. It is likely, therefore, that these proteins of DJ-12 play a role in transport of 4CBA into the cell. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 26] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Kim CK Chungbuk Natl Univ, Dept Microbiol, Heungduk Ku San 48,Gaesin Dong Cheongju 361763 South Korea Chungbuk Natl Univ, Dept Microbiol, Heungduk Ku Cheongju 361763 South Korea Chungbuk Natl Univ, Dept Pharm Cheongju 361763 South Korea Rutgers State Univ, Biotechnol Ctr Agr & Environm New Brunswick, NJ 08901 USA 28 UI - 385XK-0008 AU - Vrchotova N AU - Triska J AU - Soffel P TI - Quenching of chlorophyll a fluorescence in the micellar system containing selected aromatic compounds SO - Fresenius Environmental Bulletin 2000 Nov-Dec;9(11-12):751-758 IS - 1018-4619 MH - Fluorescence quenching MH - Chlorophyll a MH - Micellar system MH - Aromatic compounds MH - Plants MH - Leaves AB - The fluorescence quenching of chlorophyll a. in the presence of thirteen selected aromatic compounds has been studied in a micellar system containing phosphate buffer and Triton X-100 using a pulse-modulated fluorimeter. The highest relative fluorescence decline was observed for 1-nitropyrene followed by 9,10-anthraquinone, 1-amino-9,10-anthraquinone, 1-chloro-9,10-anthraquinone and pyren-1-ol. [References: 14] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences IN - Vrchotova N Acad Sci Czech Republ, Inst Landscape Ecol Branisovska 31 Ceske Budejovice 37005 Czech Republic Acad Sci Czech Republ, Inst Landscape Ecol Ceske Budejovice 37005 Czech Republic 29 UI - 384XT-0001 AU - Smith WO AU - Anderson RF AU - Moore JK AU - Codispoti LA AU - Morrison JM TI - The US Southern Ocean Joint Global Ocean Flux Study: an introduction to AESOPS SO - Deep-Sea Research Part II-Topical Studies in Oceanography 2000;47(15-16):3073-3093 IS - 0967-0645 MH - Antarctic circumpolar current MH - Phytoplankton MH - Carbon MH - Iron MH - Fronts MH - Jgofs MH - Sea AB - The United States Southern Ocean Joint Global Ocean Flux Study (JGOFS), also known as AESOPS (Antarctic Environment and Southern Ocean Process Study), focused on two distinct regions. The first was the Ross-Sea,continental shelf, where a series of six cruises collected a variety of data from October: 1996 through February 1998. The second area was the southwest Pacific sector of the Southern Ocean, spanning the Antarctic Circumpolar Current (ACC) at similar to 170 degreesW. Data were collected within this region during five cruises from September 1996 through March 1998, as well as during selected transits between New Zealand and the Ross Sea. The first results of these cruses are described in this issue. The Ross-Sea investigation extensively sampled the area along 76 degrees 30'S to elucidate the temporal patterns and processes that contribute to making this one of the Antarctic's most productive seas. Hydrographic distributions confirm that stratification is initiated early in October within the polynya, generating an environment that is favorable for phytoplankton growth. Significant spatial variations in mixed-layer depths, the timing of the onset of stratification, and the strength of the stratification existed throughout the growing season. Nutrient concentrations reflected phytoplankton uptake, and reached their seasonal minimal in early February. Chlorophyll concentrations were maximal in early January, whereas productivity was maximal in late November, which reflects the temporal uncoupling between growth and biomass accumulation in the region. Independent estimates of biogenic export suggest that majority of the flux occurred in late summer and was strongly uncoupled from phytoplankton growth, The ACC region exhibited seasonal changes that in some cases were greater than those observed in the Ross Sea. Sea ice covered much of the region south of the Polar Front in winter, and retreated rapidly in late spring and early summer. Mixed layers throughout the region shoaled in summer due to surface heating, while the addition of freshwater from melting sea ice enhanced stratification in the Seasonal Ice Zone, creating conditions favorable for phytoplankton growth. For example, silicic acid concentrations decreased from initial values as high as 65 to less than 2 muM within approximately 100 km (from 65.7 to 64.8 degreesS). Fluorescence values, however, showed less than a two-fold variation over the same distance, The vertical Aux of carbon in the Polar Front area is substantial, and marked variations in the composition of exported material exited over the region. The results provide a means whereby the controls of phytoplankton growth and organic matter flux and remineralization can be analyzed in great detail. Additional results of the AESOPS project are discussed. (C) 2000 Published by Elsevier Science Ltd. [References: 41] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Physical, Chemical & Earth Sciences IN - Smith WO Coll William & Mary, Sch Marine Sci, Virginia Inst Marine Sci Gloucester Point, VA 23062 USA Coll William & Mary, Sch Marine Sci, Virginia Inst Marine Sci Gloucester Point, VA 23062 USA Columbia Univ, Lamont Doherty Earth Observ Palisades, NY 10796 USA Natl Ctr Atmospher Res Boulder, CO 80307 USA Univ Maryland, Horn Point Environm Lab Cambridge, MD 21613 USA N Carolina State Univ, Dept Marine Earth & Atmospher Sci Raleigh, NC 27695 USA 30 UI - 384XT-0011 AU - Abbott MR AU - Richman JG AU - Letelier RM AU - Bartlett JS TI - The spring bloom in the Antarctic Polar Frontal Zone as observed from a mesoscale array of bio-optical sensors SO - Deep-Sea Research Part II-Topical Studies in Oceanography 2000;47(15-16):3285-3314 IS - 0967-0645 MH - Surface temperature data MH - Natural fluorescence MH - Southern-ocean MH - Circumpolar current MH - Chlorophyll MH - Variability MH - Sea MH - Photosynthesis MH - Drifters MH - Location AB - The US Joint Global Ocean Flux Study (JGOFS) conducted a series of survey and process studies in part to understand the processes regulating primary productivity and carbon flux in the APFZ, which is a high-nutrient, low-chlorophyll (HNLC) region. We deployed a high-resolution array of 12 moorings (average horizontal spacing 30 km) equipped with bio-optical and physical sensors to study the temporal and spatial scales of biological and physical processes in the APFZ. The moorings collected data from November 1997 to March 1998, effectively observing the growing season. Estimates of chlorophyll and sun-stimulated fluorescence/chlorophyll (F/C) were derived from the bio-optical measurements. Each mooring showed a strong spring bloom beginning in early December as the upper ocean began to stratify, with chlorophyll levels nearly quadrupling. The time series, along with ship studies, suggest that phytoplankton were initially light-limited as a result of deep, late spring mixing, followed by intense zooplankton grazing or silicate limitation, which controlled the maximum chlorophyll concentration, and finally by iron limitation, which led to increasing photoadaptive stress. These results suggest that phytoplankton in the APFZ are regulated by a confluence of processes involving light, grazing, silicate, and iron, and that models comprising a single mechanism may not be sufficient. The spring bloom in the APFZ is a transient event, persisting for only a few weeks, and therefore it is difficult to draw conclusions from sporadic ship cruises. Moreover, its spatial scales are also small so that widely spaced hydrographic stations can easily overlook critical processes. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 42] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences Current Contents(R)/Physical, Chemical & Earth Sciences IN - Abbott MR Oregon State Univ, Coll Ocean & Atmospher Sci Corvallis, OR 97331 USA Oregon State Univ, Coll Ocean & Atmospher Sci Corvallis, OR 97331 USA 31 UI - 385YT-0004 AU - Lamela T AU - Marquez-Rocha FJ TI - Phycocyanin production in seawater culture of Arthrospira maxima SO - Ciencias Marinas 2000 Dec;26(4):607-619 IS - 0185-3880 MH - Arthrospira maxima MH - Phycocyanin MH - Pigments MH - Seawater culture MH - Cyanobacterium spirulina-platensis MH - Sea-water MH - Anaerobic effluents MH - Salinity stress MH - Growth MH - Photosynthesis MH - Acclimation MH - Protein AB - Three seawater-based media were used for biomass and phycocyanin production by Arthrospira maxima. Among the three seawater-based media, growth rate and biomass were lowest in SWMAB, which is identical to SWM but includes several known essential elements (Zn, Cu, Mo, Mn). Growth in SWMX2, which has double the concentration of NaHCO3, N, P and FeEDTA than SWM, was not significantly different. Arthrospira maxima reached a biomass concentration of 2.7 +/- 0.06 g L-1 in a mineral standard medium, but <1.2 +/- 0.09 g L-1 in the seawater-based media. Pigment content in cells grown in the seawater-based media was < 2.78 +/- 0.46, < 1.85 +/- 0.18 and < 19.83 +/- 3.16 mg g(-1) cell for chlorophyll a, carotenoids and phycocyanin, respectively. The phycocyanin produced in the seawater-based media had slightly different absorption and fluorescence maxima compared to those of A. platensis. [References: 25] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences IN - Lamela T CICESE, Dept Biotecnol Marina Apartado Postal 2732 Ensenada 22830 Baja California Mexico CICESE, Dept Biotecnol Marina Ensenada 22830 Baja California Mexico 32 UI - 377EB-0001 AU - Sukharev VI AU - Vekshin NL TI - The globule diameter and some electron and conformational properties of the flavoprotein fragment of mitochondrial NADH dehydrogenase studied by fluorescence spectroscopy [Russian] SO - Bioorganicheskaia Khimiia 2000 Oct;26(10):723-727 IS - 0132-3423 MH - Correlation spectroscopy MH - Nadh dehydrogenase MH - Flavin MH - Fluorescence decay MH - Polarization MH - Tryptophan MH - Ubiquinone oxidoreductase MH - Resolved fluorescence AB - The globule dimensions and some electron and conformational properties of the flavoprotein (peripheral) fragment of the mitochondrial NADH dehydrogenase were determined by the time-resolved, phase-modulating, and polarization fluorescence spectroscopies, as well as correlated confocal microscopy. The rotational and the diffusion (translocation) diameters of the protein fragment were shown to be no less than 44 Angstrom and similar to 72 Angstrom, respectively. The diameter of protomitochondrial particles from the bovine heart, which were used for the isolation of the fraction of peripheral fragments, was no less than 2300 Angstrom. The fluorescence from tryptophan and flavin fluorophores in the fragment is strongly quenched by iron of the iron-sulfur clusters, which suggests that a strong electron-vibrational interaction of iron with Trp residues and flavin takes place. An overlapping of the electron clouds of iron-sulfur clusters, Trp residues, and flavin is likely to facilitate the electron transfer through the protein. The heat inactivation of the enzyme was accompanied by neither its substantial conformational changes, nor a considerable release of iron ions from the clusters located near the Trp residues. [References: 15] LG - Russian PT - Article SB - Current Contents(R)/Life Sciences IN - Vekshin NL Russian Acad Sci, Inst Cell Biophys Pushchino 142290 Moscow Oblast Russia Russian Acad Sci, Inst Cell Biophys Pushchino 142290 Moscow Oblast Russia 33 UI - 386PD-0022 AU - Aagaard A AU - Gilderson G AU - Mills DA AU - Ferguson-Miller S AU - Brzezinski P TI - Redesign of the proton-pumping machinery of cytochrome c oxidase: Proton pumping does not require Glu(I-286) SO - Biochemistry 2000 Dec 26;39(51):15847-15850 IS - 0006-2960 MH - Rhodobacter-sphaeroides MH - Paracoccus-denitrificans MH - Thermus-thermophilus MH - Escherichia-coli MH - Translocation MH - Purification MH - Glutamic-acid-286 MH - Glutamate-286 MH - Resolution MH - Mechanism AB - One of the putative proton-transfer pathways leading from solution toward the binuclear center in many cytochrome c oxidases is the D-pathway, so-called because it starts with a highly conserved aspartate [D(I-132)] residue. Another highly conserved amino acid residue in this pathway, glutamate(I-286), has been indicated to play a central role in the proton-pumping machinery of mitochondrial-type enzymes, a role that requires a movement of the side chain between two distinct positions. In the present work we have relocated the glutamate to the opposite side of the proton-transfer pathway by constructing the double mutant EA(I-286)/IE(I-112). This places the side chain in about the same position in space as in the original enzyme, but does not allow for the same type of movement. The results show that the introduction of the second-site mutation, IE(I-112), in the EA(I-286) mutant enzyme results in an increase of the enzyme activity by a factor of >10. In addition, the double mutant enzyme pumps similar to0.4 proton per electron. This observation restricts the number of possible mechanisms for the operation of the redox-driven proton pump. The proton-pumping machinery evidently does require the presence of a protonatable/polar residue at a specific location in space, presumably to stabilize an intact water chain. However, this residue does not necessarily have to be at a strictly conserved location in the amino acid sequence. In addition, the results indicate that E(I-286) is not the "proton gate" of cytochrome c oxidase controlling the flow of pumped protons from one to the other side of the membrane. [References: 32] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Brzezinski P Stockholm Univ, Arrhenius Lab, Dept Biochem SE-10691 Stockholm Sweden Stockholm Univ, Arrhenius Lab, Dept Biochem SE-10691 Stockholm Sweden Univ Gothenburg, Dept Biochem & Biophys SE-40530 Gothenburg Sweden Michigan State Univ, Dept Biochem E Lansing, MI 48824 USA 34 UI - 386PD-0059 AU - Reimers JR AU - Hughes JM AU - Hush NS TI - Modeling the bacterial photosynthetic reaction center 3: Interpretation of effects of site-directed mutagenesis on the special-pair midpoint potential SO - Biochemistry 2000 Dec 26;39(51):16185-16189 IS - 0006-2960 MH - Primary electron-donor MH - Rhodobacter-sphaeroides MH - Radical cations MH - Photosystem-ii MH - Energy computations MH - Purple bacteria MH - Mixed-valence MH - Spectroscopy MH - Resonance MH - Cofactors AB - Interpretation of changes in midpoint potential of the "special pair" in bacterial photosynthetic reaction centers caused by site-directed mutagenesis is discussed in terms of a simple tight-binding model which relates them to concomitant variations in spin distribution between the two bacteriochlorophyll molecules of the special pair. Our analysis improves on previous similar ones by Alien and co-workers [Artz, K., Williams, J. C., Allen, J. P., Lendzian, F., Rautter, J., and Lubitz, W. (1997) Proc. Nad Acad. Sci. U.S.A. 94, 13582; Ivancich, A., Artz, K., Williams, J. C., Alien, J. P., and Mattioli, T. A. (1998) Biochemistry 37, 11812] in that it is both more complete, including electron-phonon coupling, and more accurate. It is applied to analyze data for a series of M160 mutants of Rhodobacter sphaeroides, yielding a value of 0.18 +/- 0.03 eV for the electronic coupling energy between the highest occupied levels of the two bacteriochlorophylls in the wild-type and a value of the energy offset E-o between the highest occupied molecular orbitals of the L and M bacteriochlorophylls of 0.14 +/- 0.03 eV. For a mutant in which the electron hole in the special pair cation is located entirely on the reactive (L) side, a potential of 641 +/- 30 mV with respect to the normal hydrogen electrode is predicted. This agrees well with the average value ca. 650 mV observed for the heterodimer mutant HL(M202) in which the bacteriochlorophyll on the unreactive M side has been replaced by a bacteriopheophytin, causing extensive charge localization. However, the deduced coupling is found to be very sensitive to small changes in the assumptions used in the model, and various important chemical effects remain to be included. [References: 29] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Hush NS Univ Sydney, Sch Chem Sydney NSW 2006 Australia Univ Sydney, Sch Chem Sydney NSW 2006 Australia Univ Sydney, Dept Biochem Sydney NSW 2006 Australia 35 UI - 386PD-0062 AU - Shinkarev VP AU - Ugulava NB AU - Crofts AR AU - Wraight CA TI - DCCD inhibits the reactions of the iron-sulfur protein in Rhodobacter sphaeroides chromatophores SO - Biochemistry 2000 Dec 26;39(51):16206-16212 IS - 0006-2960 MH - Cytochrome bc(1) complex MH - Photosynthetic reaction-center MH - Bovine heart-mitochondria MH - Proton-pumping activity MH - Rhodopseudomonas-sphaeroides MH - Electron-transfer MH - Q-cycle MH - B-c1 complex MH - Oxidation MH - Residues AB - N,N'-dicyclohexylcarbodiimide (DCCD) has been reported to inhibit proton translocation by cytochrome bc(1) and b(6)f complexes without significantly altering the rate of electron transport, a process referred to as decoupling. To understand the possible role of DCCD in inhibiting the protonogenic reactions of cytochrome bc(1) complex, we investigated the effect of DCCD modification on flash-induced electron transport and electrochromic bandshift of carotenoids in Rb. sphaeroides chromatophores. DCCD has two distinct effects on phase III of the electrochromic bandshift of carotenoids reflecting the electrogenic reactions of the bc(1) complex. At low concentrations, DCCD increases the magnitude of the electrogenic process because of a decrease in the permeability of the membrane, probably through inhibition of FoF1. At higher concentrations (>150 muM), DCCD slows the development of phase III of the electrochromic shift from about 3 ms in control preparations to about 23 ms at 1.2 mM DCCD, without significantly changing the amplitude. DCCD treatment of chromatophores also slows down the kinetics of flash-induced reduction of both cytochromes b and c, from 1.5-2 ms in control preparations to 8-10 ms at 0.8 mM DCCD. Parallel slowing of the reduction of both cytochromes indicates that DCCD treatment modifies the reaction of QH(2) oxidation at the Q(o), site. Despite the similarity in the kinetics of both cytochromes, the onset of cytochrome c re-reduction is delayed 1-2 ms in comparison to cytochrome b reduction, indicating that DCCD inhibits the delivery of electrons from quinol to heme c(1). We conclude that DCCD treatment of chromatophores leads to modification of the rate of Q(o)H(2) oxidation by the iron-sulfur protein (ISP) as well as the donation of electrons from ISP to c(1), and we discuss the results in the context of the movement of ISP between the Q(o), site and cytochrome c(1). [References: 48] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Wraight CA Univ Illinois, Dept Biochem, Roger Adams Lab 419 600 S Mathews Ave Urbana, IL 61801 USA Univ Illinois, Dept Biochem, Roger Adams Lab 419 Urbana, IL 61801 USA Univ Illinois, Dept Plant Biol Urbana, IL 61801 USA 36 UI - 386PD-0064 AU - Westphal KL AU - Lydakis-Simantiris N AU - Cukier RI AU - Babcock GT TI - Effects of Sr2+-substitution on the reduction rates of Y-z(center dot) in PSII membranes - Evidence for concerted hydrogen-atom transfer in oxygen evolution SO - Biochemistry 2000 Dec 26;39(51):16220-16229 IS - 0006-2960 MH - Photosynthetic water oxidation MH - Photosystem-ii preparations MH - Coupled electron-transfer MH - Ray-absorption spectroscopy MH - Tertiary alkyl radicals MH - O bond formation MH - Tyrosine y-z MH - Manganese cluster MH - Evolving complex MH - O-2-evolving complex AB - Several groups have recently investigated the kinetic effects of biochemical treatments, site-directed mutagenesis, or substitution of essential cofactors on the stepwise, water-oxidizing chemistry catalyzed by Photosystem II. Consistently, these studies show evidence for a slowing of the final, oxygen-releasing step, S-3 (-->) S-0, of the catalytic cycle. To a degree, some of this work also shows a slowing of the earlier S-state transitions. To study these processes in more detail, we have investigated the effect of replacing Ca2+ with Sr2+ on the rates of the S-state transitions by using time-resolved electron paramagnetic resonance. The results show a slowdown of the last transition in the cycle, consistent with a report from Boussac et al. [Boussac, A., Setif, P., and Rutherford, A. W. (1992) Biochemistry-31, 1224-1234], and of the earlier S-state transitions as well, which suggests that a common molecular mechanism is at work and that Sr2+ is less effective than Ca2+ in supporting it. While the oxidation of Y-z by P-680(+) has been extensively studied and can be understood within the context of nonadiabatic electron tunneling combined with rapid, non-rate-limiting proton transfer in the hole-system [Tommos, C., and Babcock, G. T. (2000) Biochim. Biophys. Acta 1458, 199], the reduction of Y-z(.) by the Mn cluster cannot be described effectively by a nonadiabatic electron-transfer formalism. This indicates that this reaction is rate limited by processes other than electron tunneling. We discuss our results for Y-z(.) reduction and those of others for the activation parameters (E-a, A, KIE, and rates) associated with this process, in terms of both sequential and concerted proton-coupled, electron transfer. Our analysis indicates that concerted hydrogen-atom transfer processes best explain the observed characteristics of the S-state advances. [References: 89] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Babcock GT Michigan State Univ, Dept Chem E Lansing, MI 48824 USA Michigan State Univ, Dept Chem E Lansing, MI 48824 USA 37 UI - 386PD-0068 AU - Ginet N AU - Lavergne J TI - Interactions between the donor and acceptor sides in bacterial reaction centers SO - Biochemistry 2000 Dec 26;39(51):16252-16262 IS - 0006-2960 MH - Photosynthetic reaction centers MH - Direct charge recombination MH - Secondary-electron transfer MH - Induced structural-changes MH - Rhodobacter-sphaeroides MH - Rhodopseudomonas-viridis MH - Quinone complex MH - Proton-transfer MH - Herbicide activity MH - Photosystem-ii AB - The apparent equilibrium constant K'(2) for electron transfer between the primary (Q(A)) and secondary (Q(B)) quinone accepters of the reaction center was measured in chromatophores of Rhodobacter capsulatus. In the presence of the oxidized primary donor P+, we obtained a value of K'(2)(P+) approximate to 100 at pH 7.2, based on the rates of recombination from P(+)Q(A)(-) and P(+)Q(B)(-). K'(2) was also measured in the presence of reduced P, from the damping of semiquinone oscillations during a series of single turnover flashes. A 5-fold smaller value, K'(2)(P) approximate to 20, was found. Additional information on the interactions between the donor and acceptor sides was obtained by measuring the shift of the midpoint potential of P caused by the presence of Q(B)(-) or Q(A)(-)S (where S indicates the presence of the inhibitor stigmatellin). A stabilization of the oxidized state P+ was observed in both instances, by 10 mV for Q(B)(-) and 30 mV for Q(A)(-)S. The larger stabilization of P(+)Q(A)(-)S with respect to P(+)Q(B)(-) does not account for the effect of P+/P on K'(2). Analysis of these results indicates that the interactions between P+/P and Q(A)/Q(A)(-) are markedly modified depending on the occupancy of the Q(B) pocket by ubiquinone or by stigmatellin. We propose that the large value of K'(2)(P+) results essentially from a conformational destabilization of the P(+)Q(A)(-) state, that is relieved when the proximal site of the Q(B) pocket is occupied by stigmatellin. [References: 44] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Lavergne J CEN Cadarache, DEVM, LBC F-13108 St Paul Durance France CEN Cadarache, DEVM, LBC F-13108 St Paul Durance France 38 UI - 385VC-0023 AU - Jensen PE AU - Reid JD AU - Hunter CN TI - Modification of cysteine residues in the ChlI and ChlH subunits of magnesium chelatase results in enzyme inactivation SO - Biochemical Journal 2000 Dec 1;352(Part 2):435-441 IS - 0264-6021 MH - Atpase MH - Chlorophyll biosynthesis MH - Cysteine modification MH - Mg2+ chelatase MH - Subunit interaction MH - Synechocystis MH - Tetrapyrrole MH - Developing cucumber chloroplasts MH - Phosphate exchange activities MH - Protoporphyrin-ix chelatase MH - Synechocystis pcc6803 MH - Escherichia-coli MH - Mg-chelatase MH - Rhodobacter-sphaeroides MH - Chlorobium-vibrioforme MH - Thiol-groups MH - Xantha-g AB - The enzyme magnesium protoporphyrin chelatase catalyses the insertion of magnesium into protoporphyrin, the first committed step in chlorophyll biosynthesis. Magnesium chelatase from the cyanobacterium Synechocystis PCC6803 has been reconstituted in a highly active state as a result of purifying the constituent proteins from strains of Escherichia coli that overproduce the ChlH, ChlI and ChlD subunits. These individual subunits were analysed for their sensitivity to N-ethylmaleimide (NEM), in order to assess the roles that cysteine residues play in the partial reactions that comprise the catalytic cycle of Mg2+ chelatase, such as the ATPase activity of ChlI, and the formation of ChlI-ChlD-MgATP and ChlH-protoporphyrin complexes. It was shown that NEM binds to ChlI and inhibits the ATPase activity of this subunit, and that prior incubation with MgATP affords protection against inhibition. Quantitative analysis of the effects of NEM binding on ChlI-catalysed ATPase activity showed that three out of four thiols per ChlI molecule are available to react with NEM, but only one cysteine residue per ChlI subunit is essential for ATPase activity. In contrast, the cysteines in ChlD are not essential for Mg2+ chelatase activity, and the formation of the ChlI-ChlD-ATP complex can proceed with NEM-treated ChlI. Neither the ATPase activity of Chi nor NEM-modifiable cysteines are therefore required to form the ChlI-ChlD-MgATP complex. However, this complex cannot catalyse magnesium chelation in the presence of the ChlH subunit, protoporphyrin and Mg2+ ions. The simplest explanation for this is that in an intact Mg2+ chelatase complex the ATPase activity of ChlI drives the chelation process. NEM binds to ChlH and inhibits the chelation reaction, and this effect can be partially alleviated by pre-incubating ChlH with magnesium and ATP. We conclude that cysteine residues play an important role in the chelation reaction, in respect of the ChlI-MgATP association, ATP hydrolysis and in the interaction of ChlH with MgATP and protoporphyrin IX. [References: 22] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Hunter CN Univ Sheffield, Krebs Inst Biomolec Res, Dept Mol Biol & Biotechnol Sheffield S10 2TN S Yorkshire England Univ Sheffield, Krebs Inst Biomolec Res, Dept Mol Biol & Biotechnol Sheffield S10 2TN S Yorkshire England Univ Sheffield, Robert Hill Inst Photosynth, Dept Mol Biol & Biotechnol Sheffield S10 2TN S Yorkshire England Royal Vet & Agr Univ, Dept Plant Biol, Plant Biochem Lab DK-1871 Frederiksberg Denmark 39 UI - 384XG-0012 AU - Miranda JH AU - Joyce DC AU - Hetherington SE AU - Jones PN TI - Cold-storage-induced changes in chlorophyll fluorescence of kangaroo paw Bush Dawn flowers SO - Australian Journal of Experimental Agriculture 2000;40(8):1151-1155 IS - 0816-1089 MH - Anigozanthos MH - Chilling injury MH - Cut flower MH - Vase life AB - Effects on vase life and chlorophyll fluorescence were evaluated for kangaroo paw Bush Dawn flowers harvested from 3 growth environments and kept at 3 storage temperatures for 4 storage periods. Flowers were grown in a glasshouse, shadehouse and in the open. Harvested flowers were stored at 0, 7.5 or 13 degreesC for 1, 2, 3 or 4 weeks. Minimum fluorescence values decreased progressively from 0.103 to 0.078 as storage temperatures increased from 0 to 13 degreesC. Relative fluorescence ratios of stored kangaroo paw flowers were altered significantly in response to storage temperature, storage duration and growth environment. Relative fluorescence ratios decreased progressively from 0.778 to 0.649 with increasing storage duration from 1 to 4 weeks. Relative fluorescence values were 0.688, 0.784 and 0.711 for 0, 7.5 and 13 degreesC storage temperatures, respectively. Minimum fluorescence did not differ among the growth environments, but relative fluorescence was highest for the shadehouse (0.760) and lowest for the open (0.695). Vase life was also influenced by storage temperature, storage duration and flower source. Main effect vase lives of flowers were 6.6, 7.2 and 3.4 days for 0, 7.5 and 13 degreesC storage temperatures, respectively. Shorter vase life after storage at 0 than at 7.5 degreesC indicates that Bush Dawn is chilling sensitive. Post-storage longevity of flowers from the shadehouse (6.5 days) and glasshouse (6.3 days) was greater than from the open (4.2 days). Relative fluorescence values, which decreased in a linear manner for all storage temperatures as storage duration increased, were significantly correlated with the vase life. [References: 15] LG - English PT - Article SB - Current Contents(R)/Agriculture, Biology & Environmental Sciences IN - Joyce DC Cranfield Univ, Postharvest Horp Lab Silsoe MK45 4DT Beds England Cranfield Univ, Postharvest Horp Lab Silsoe MK45 4DT Beds England Univ Queensland, Sch Land & Food Lawes Qld Australia CSIRO, Div Trop Agr, Biometr Grp Long Pocket Qld 4068 Australia 40 UI - 385LZ-0006 AU - Guan ZZ AU - Xiao KQ AU - Zeng XY AU - Long YG AU - Cheng YH AU - Jiang SF AU - Wang YN TI - Changed cellular membrane lipid composition and lipid peroxidation of kidney in rats with chronic fluorosis SO - Archives of Toxicology 2000 Dec;74(10):602-608 IS - 0340-5761 MH - Lipid MH - Fatty acid MH - Fluorosis MH - Lipid peroxidation MH - Kidney MH - Dolichyl-phosphate MH - Sodium-fluoride MH - Brain MH - Cholesterol MH - Ubiquinone MH - Tissues MH - Liver AB - An animal model of chronic fluorosis was produced by subjecting Wistar rats to high doses of fluoride in drinking water for a prolonged period. Phospholipid and neutral lipid contents in rat kidney were then analyzed by high-performance liquid chromatography (HPLC), and fatty acid compositions from individual phospholipids were measured by gas chromatography. Lipid peroxidation was detected by the thiobarbituric-acid-reactive substance assay. Results showed that the total phospholipid content significantly decreased in the kidney of the rats treated with high doses of fluoride and the main species influenced were phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Decreased proportions of polyunsaturated fatty acids were observed in PE and PC in kidney of fluoride-treated animals compared to controls. No changes could be detected in the amounts of cholesterol and dolichol in kidneys between the rats treated with fluoride and controls. A significant decrease of ubiquinone in rat kidney was observed in the groups treated with excessive fluoride. High levels of lipid peroxidation were detected in kidney of the rats with fluorosis. It is plausible that the specific modification of lipid composition results from lipid peroxidation. The oxidative stress and modification of cellular membrane lipids may be involved in the pathogenesis of chronic fluorosis and provide a possible explanation for the gross system damage observed in the body, especially in soft tissues and organs. [References: 42] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Guan ZZ Huddinge Hosp, Karolinska Inst, Dept NEUROTEC, Div Mol Neuropharmacol S-14186 Huddinge Sweden Huddinge Hosp, Karolinska Inst, Dept NEUROTEC, Div Mol Neuropharmacol S-14186 Huddinge Sweden Guiyang Med Coll, Dept Pathol Guiyang 550004 Guizhou Peoples R China Guiyang Med Coll, Dept Sci Res Adm Guiyang 550004 Guizhou Peoples R China Univ Stockholm, Dept Biochem S-10691 Stockholm Sweden 41 UI - 384NV-0006 AU - Milewski S AU - Mignini F AU - Prasad R AU - Borowski E TI - Unusual susceptibility of a multidrug-resistant yeast strain to peptidic antifungals SO - Antimicrobial Agents & Chemotherapy 2001 Jan;45(1):223-228 IS - 0066-4804 MH - Candida-albicans MH - Saccharomyces-cerevisiae MH - Transport gene MH - P-glycoprotein MH - Drug-resistance MH - Cloning MH - Protein MH - Binding MH - Mode MH - Mechanisms AB - The susceptibility of Saccharomyces cerevisiae JG436 multidrug transporter deletion mutant, Delta pdr5, to several antifungal agents was compared to that of JG436-derived JGCDR1 and JGCaMDR1 transformants, harboring the CDR1 and CaMDR1 genes, encoding the main drug-extruding membrane proteins of Candida albicans. The JGCDR1 and JGCaMDR1 yeasts demonstrated markedly diminished susceptibility to the azole antifungals, terbinafine and cycloheximide, while that to amphotericin B was unchanged, Surprisingly, JGCDR1 but not JGCaMDR1 cells showed enhanced susceptibility to peptidic antifungals, rationally designed compounds containing inhibitors of glucosamine-6-phosphate synthase. It was found that these antifungal oligopeptides, as well as model oligopeptides built of proteinogenic amino acids, were not effluxed from JGCDR1 cells, Moreover, they were taken up by these cells at rates two to three times higher than by JG436. The tested oligopeptides were rapidly cleaved to constitutive amino acids by cytoplasmic peptidases, Studies on the mechanism of the observed phenomenon suggested that an additive proton motive force generated by Cdr1p stimulated uptake of oligopeptides into JGCDR1 cells, thus giving rise to the higher antifungal activity of FMDP [N-3-(4-methoxyfumaroyl)-L-2,3-diaminopropanoic acid]-peptides. [References: 37] LG - English PT - Article SB - Current Contents(R)/Life Sciences IN - Milewski S Gdansk Tech Univ, Dept Pharmaceut Technol & Biochem 11-12 Narutowicza St PL-80952 Gdansk Poland Gdansk Tech Univ, Dept Pharmaceut Technol & Biochem PL-80952 Gdansk Poland Univ Camerino, Dept Mol Cellular & Anim Biol I-62032 Camerino Italy Jawaharlal Nehru Univ, Sch Life Sci New Delhi 110067 India 42 UI - 385NH-0004 AU - Dalbey RE AU - Kuhn A TI - Evolutionarily related insertion pathways of bacterial, mitochondrial, and thylakoid membrane proteins [Review] SO - Annual Review of Cell & Developmental Biology 2000;16:51-+ IS - 1081-0706 MH - Sec translocase MH - Assembly MH - Srp complex MH - Signal sequence MH - Membrane insertion MH - Signal-recognition particle MH - Positively charged residues MH - M13 procoat protein MH - Coli leader peptidase MH - Cytochrome-c-oxidase MH - Proton motive force MH - Chloroplastic envelope membranes MH - Stop-transfer sequence MH - Amino-acid-residues MH - Major coat protein AB - The inner membranes of eubacteria and mitochondria, as well as the chloroplast thylakoid membrane, contain essential proteins that function in oxidative phosphorylation and electron transport processes or in photosynthesis. Because most of the organellar proteins are nuclear encoded, they are synthesized in the cytoplasm and subsequently imported into the organelle before they are inserted into the membrane. This review focuses on the pathways of protein insertion into the inner membrane of eubacteria and mitochondria and into the chloroplast thylakoid membrane. In many respects, insertion of proteins into the inner membrane of bacteria is a process similar to that used by proteins of the thylakoid membrane. In both of these systems a signal recognition particle (SRP) and a SecYE-translocase are involved, as in translocation into the endoplasmic reticulum. The pathway of proteins into the mitochondrial membranes appears to be different in that it involves no SecYE-like components. A conservative pathway, recently identified in mitochondria, involves the Oral protein for the insertion of proteins from the matrix. The presence of Oral homologues in eubacteria and chloroplasts suggests that this pathway is evolutionarily conserved. [References: 229] LG - English PT - Review SB - Current Contents(R)/Life Sciences IN - Dalbey RE Ohio State Univ, Dept Chem 100 W 18th Ave Columbus, OH 43210 USA Ohio State Univ, Dept Chem Columbus, OH 43210 USA Univ Hohenheim, Inst Microbiol & Mol Biol D-70599 Stuttgart Germany