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Grieco M, Roustan V, Dermendjiev G, Rantala S, Jain A, Leonardelli M, Neumann K, Berger V, Engelmeier D, Bachmann G, Ebersberger I, Aro E, Weckwerth W, Teige M. Adjustment of photosynthetic activity to drought and fluctuating light in wheat. PLANT, CELL & ENVIRONMENT 2020; 43:1484-1500. [PMID: 32176335 PMCID: PMC7384038 DOI: 10.1111/pce.13756] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 03/02/2020] [Indexed: 05/24/2023]
Abstract
Drought is a major cause of losses in crop yield. Under field conditions, plants exposed to drought are usually also experiencing rapid changes in light intensity. Accordingly, plants need to acclimate to both, drought and light stress. Two crucial mechanisms in plant acclimation to changes in light conditions comprise thylakoid protein phosphorylation and dissipation of light energy as heat by non-photochemical quenching (NPQ). Here, we analyzed the acclimation efficacy of two different wheat varieties, by applying fluctuating light for analysis of plants, which had been subjected to a slowly developing drought stress as it usually occurs in the field. This novel approach allowed us to distinguish four drought phases, which are critical for grain yield, and to discover acclimatory responses which are independent of photodamage. In short-term, under fluctuating light, the slowdown of NPQ relaxation adjusts the photosynthetic activity to the reduced metabolic capacity. In long-term, the photosynthetic machinery acquires a drought-specific configuration by changing the PSII-LHCII phosphorylation pattern together with protein stoichiometry. Therefore, the fine-tuning of NPQ relaxation and PSII-LHCII phosphorylation pattern represent promising traits for future crop breeding strategies.
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Affiliation(s)
- Michele Grieco
- Ecogenomics and Systems BiologyUniversity of ViennaViennaAustria
- Department of Genebank, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK)SeelandGermany
| | - Valentin Roustan
- Ecogenomics and Systems BiologyUniversity of ViennaViennaAustria
| | | | - Sanna Rantala
- Molecular Plant BiologyUniversity of TurkuTurkuFinland
| | - Arpit Jain
- Applied Bioinformatics GroupInstitute of Cell Biology and Neuroscience, Goethe‐University FrankfurtFrankfurtGermany
| | | | - Kerstin Neumann
- Department of Genebank, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK)SeelandGermany
| | - Vitus Berger
- Ecogenomics and Systems BiologyUniversity of ViennaViennaAustria
| | - Doris Engelmeier
- Ecogenomics and Systems BiologyUniversity of ViennaViennaAustria
| | - Gert Bachmann
- Ecogenomics and Systems BiologyUniversity of ViennaViennaAustria
| | - Ingo Ebersberger
- Applied Bioinformatics GroupInstitute of Cell Biology and Neuroscience, Goethe‐University FrankfurtFrankfurtGermany
- Senckenberg Biodiversity and Climate Research Centre (S‐BIK‐F)FrankfurtGermany
- LOEWE Center for Translational Biodiversity GenomicsFrankfurtGermany
| | - Eva‐Mari Aro
- Molecular Plant BiologyUniversity of TurkuTurkuFinland
| | - Wolfram Weckwerth
- Ecogenomics and Systems BiologyUniversity of ViennaViennaAustria
- Vienna Metabolomics Center (VIME)University of ViennaViennaAustria
| | - Markus Teige
- Ecogenomics and Systems BiologyUniversity of ViennaViennaAustria
- Max Perutz Labs, Department of Biochemistry & Cell BiologyUniversity of ViennaViennaAustria
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2
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Cramer WA. Structure-function of the cytochrome b 6f lipoprotein complex: a scientific odyssey and personal perspective. PHOTOSYNTHESIS RESEARCH 2019; 139:53-65. [PMID: 30311133 PMCID: PMC6510485 DOI: 10.1007/s11120-018-0585-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 09/15/2018] [Indexed: 05/04/2023]
Abstract
Structure-function studies of the cytochrome b6f complex, the central hetero-oligomeric membrane protein complex in the electron transport chain of oxygenic photosynthesis, which formed the basis for a high-resolution (2.5 Å) crystallographic solution of the complex, are described. Structure-function differences between the structure of subunits of the bc complexes, b6f, and bc1 from mitochondria and photosynthetic bacteria, which are often assumed to function identically, are discussed. Major differences which suggest that quinone-dependent electron transport pathways can vary in b6f and bc1 complexes are as follows: (a) an additional c-type heme, cn, and bound single copies of chlorophyll a and β-carotene in the b6f complex; and (b) a cyclic electron transport pathway that encompasses the b6f and PSI reaction center complexes. The importance of including lipid in crystallization of the cytochrome complex, or with any hetero-oligomeric membrane protein complex, is emphasized, and consequences to structure-function of b6f being a lipoprotein complex discussed, including intra-protein dielectric heterogeneity and resultant pathways of trans-membrane electron transport. The role of the b6f complex in trans-membrane signal transduction from reductant generated on the p-side of the electron transport chain to the regulation of light energy to the two photosystems by trans-side phosphorylation of the light-harvesting chlorophyll protein is presented. Regarding structure aspects relevant to plastoquinol-quinone entrance-egress: (i) modification of the p-side channel for plastoquinone access to the iron-sulfur protein would change the rate-limiting step in electron transport; (ii) the narrow niche for entry of plastoquinol into b6f from the PSII reaction center complex would seem to require close proximity between the complexes.
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Affiliation(s)
- William A Cramer
- Department of Biological Sciences, Purdue University, Hockmeyer Building for Structural Biology, West Lafayette, IN, 47907, USA.
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3
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Xu K, Racine F, He Z, Juneau P. Impacts of hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor (mesotrione) on photosynthetic processes in Chlamydomonas reinhardtii. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 244:295-303. [PMID: 30343230 DOI: 10.1016/j.envpol.2018.09.121] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 08/27/2018] [Accepted: 09/24/2018] [Indexed: 06/08/2023]
Abstract
Mesotrione, an herbicide increasingly found in aquatic systems due to its increased application frequency in corn fields, is an inhibitor of the p-hydroxyphenylpyruvate dioxygenase (HPPD), a key enzyme for plastoquinone-9, α-tocopherol and indirectly for carotenoid biosynthesis. The direct effect of mesotrione on plastoquinone-9 and α-tocopherol synthesis and their degradation rates are well documented, but few information exists on its action on photosynthetic processes under various light intensities. We therefore investigated the photosynthetic activity, energy dissipation processes, pigment composition and α-tocopherol content when Chlamydomonas reinhardtii were exposed to mesotrione for 24 h under low light condition and then the impacts of HL treatment (75 min) were also investigated. Under low light growth conditions, mesotrione did not induce PSII photoinhihition, while substantially decreased Car:Chl-a ratio, maximal energy-dependant quenching and state 1 to state 2 transition. Under high light conditions (HL), PSII activity was highly decreased in presence of mesotrione, and the non-photochemical energy dissipation processes were drastically affected in these conditions compared to the HL treatment alone. Mesotrinone also prevent the complete recovery of PSII damage caused by HL. Light condition seems therefore to be a non-negligible factor modulating mesotrione toxicity, and this has an obvious importance in agricultural waterbodies where phytoplankton is subjected to fluctuating light intensities.
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Affiliation(s)
- Kui Xu
- School of Environmental Science and Engineering, Environmental Microbiomics Research Center, Sun Yat-sen University, Guangzhou, 510006, China
| | - Francis Racine
- Department of Biological Sciences, GRIL-TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Université du Québec à Montréal, Succ. Centre-Ville, Montréal, Québec, Canada
| | - Zhili He
- School of Environmental Science and Engineering, Environmental Microbiomics Research Center, Sun Yat-sen University, Guangzhou, 510006, China
| | - Philippe Juneau
- Department of Biological Sciences, GRIL-TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Université du Québec à Montréal, Succ. Centre-Ville, Montréal, Québec, Canada.
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Yamori W, Shikanai T. Physiological Functions of Cyclic Electron Transport Around Photosystem I in Sustaining Photosynthesis and Plant Growth. ANNUAL REVIEW OF PLANT BIOLOGY 2016; 67:81-106. [PMID: 26927905 DOI: 10.1146/annurev-arplant-043015-112002] [Citation(s) in RCA: 284] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The light reactions in photosynthesis drive both linear and cyclic electron transport around photosystem I (PSI). Linear electron transport generates both ATP and NADPH, whereas PSI cyclic electron transport produces ATP without producing NADPH. PSI cyclic electron transport is thought to be essential for balancing the ATP/NADPH production ratio and for protecting both photosystems from damage caused by stromal overreduction. Two distinct pathways of cyclic electron transport have been proposed in angiosperms: a major pathway that depends on the PROTON GRADIENT REGULATION 5 (PGR5) and PGR5-LIKE PHOTOSYNTHETIC PHENOTYPE 1 (PGRL1) proteins, which are the target site of antimycin A, and a minor pathway mediated by the chloroplast NADH dehydrogenase-like (NDH) complex. Recently, the regulation of PSI cyclic electron transport has been recognized as essential for photosynthesis and plant growth. In this review, we summarize the possible functions and importance of the two pathways of PSI cyclic electron transport.
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Affiliation(s)
- Wataru Yamori
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan;
- Precursory Research for Embryonic Science and Technology (PRESTO) and
| | - Toshiharu Shikanai
- Core Research for Evolutionary Science and Technology (CREST), Japan Science and Technology Agency, Kawaguchi 332-0012, Japan
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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5
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Kangasjärvi S, Tikkanen M, Durian G, Aro EM. Photosynthetic light reactions--an adjustable hub in basic production and plant immunity signaling. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2014; 81:128-34. [PMID: 24361390 DOI: 10.1016/j.plaphy.2013.12.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 12/03/2013] [Indexed: 05/09/2023]
Abstract
Photosynthetic efficiency is a key trait that influences the sustainable utilization of plants for energy and nutrition. By now, extensive research on photosynthetic processes has underscored important structural and functional relationships among photosynthetic thylakoid membrane protein complexes, and their roles in determining the productivity and stress resistance of plants. Photosystem II photoinhibition-repair cycle, for example, has arisen vital in protecting also Photosystem I against light-induced damage. Availability of highly sophisticated genetic, biochemical and biophysical tools has greatly expanded the catalog of components that carry out photoprotective functions in plants. On thylakoid membranes, these components encompass a network of overlapping systems that allow delicate regulation of linear and cyclic electron transfer pathways, balancing of excitation energy distribution between the two photosystems and dissipation of excess light energy in the antenna system as heat. An increasing number of reports indicate that the above mentioned mechanisms also mediate important functions in the regulation of biotic stress responses in plants. Particularly the handling of excitation energy in the light harvesting II antenna complexes appears central to plant immunity signaling. Comprehensive understanding of the underlying mechanisms and regulatory cross-talk, however, still remain elusive. This review highlights the current understanding of components that regulate the function of photosynthetic light reactions and directly or indirectly also modulate disease resistance in higher plants.
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Affiliation(s)
| | - Mikko Tikkanen
- Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland
| | - Guido Durian
- Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland
| | - Eva-Mari Aro
- Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland.
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6
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Nucleotide sequence of the gene for pre-apocytochrome f in the spinach plastid chromosome. Curr Genet 2013; 8:551-7. [PMID: 24177957 DOI: 10.1007/bf00410443] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/1984] [Indexed: 10/26/2022]
Abstract
We have characterized a cloned fragment of the spinach plastid chromosome encoding the gene for apocytochrome f. Northern blot analysis and hybrid selection translation discloses that the gene is expressed. From the nucleotide sequence, we deduce that the protein contains 285 amino acids and an amino-terminal signal sequence of 35 amino acid residues. The calculated molecular mass of pre-apocytochrome f is 35.3 kd. The clustering of hydrophobic residues indicates that the processed protein (31.3 kd) possesses only a single anchoring transmembrane domain close to the C terminus, and that 75% of the polypeptide chain including the heme-binding site protrudes into the thylakoid lumen. This topology resembles that reported for beef heart mitochondrial cytochrome c1.
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7
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Carraretto L, Formentin E, Teardo E, Checchetto V, Tomizioli M, Morosinotto T, Giacometti GM, Finazzi G, Szabó I. A Thylakoid-Located Two-Pore K+ Channel Controls Photosynthetic Light Utilization in Plants. Science 2013; 342:114-8. [DOI: 10.1126/science.1242113] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The size of the light-induced proton motive force (pmf) across the thylakoid membrane of chloroplasts is regulated in response to environmental stimuli. Here, we describe a component of the thylakoid membrane, the two-pore potassium (K+) channel TPK3, which modulates the composition of the pmf through ion counterbalancing. Recombinant TPK3 exhibited potassium-selective channel activity sensitive to Ca2+ and H+. In Arabidopsis plants, the channel is found in the thylakoid stromal lamellae. Arabidopsis plants silenced for the TPK3 gene display reduced growth and altered thylakoid membrane organization. This phenotype reflects an impaired capacity to generate a normal pmf, which results in reduced CO2 assimilation and deficient nonphotochemical dissipation of excess absorbed light. Thus, the TPK3 channel manages the pmf necessary to convert photochemical energy into physiological functions.
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8
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Antal TK, Kukarskikh GP, Bulychev AA, Tyystjärvi E, Krendeleva T. Antimycin A effect on the electron transport in chloroplasts of two Chlamydomonas reinhardtii strains. PLANTA 2013; 237:1241-1250. [PMID: 23354456 DOI: 10.1007/s00425-013-1843-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 01/07/2013] [Indexed: 06/01/2023]
Abstract
The effects of antimycin A on the redox state of plastoquinone and on electron donation to photosystem I (PS I) were studied in sulfur-deprived Chlamydomonas reinhardtii cells of the strains cc406 and 137c. We found that this reagent suppresses cyclic electron flow around PS I in the cc406 strain, whereas this inhibitory effect was completely absent in the 137c strain. In the latter strain, antimycin A induced rapid reduction of plastoquinone in the dark and considerably enhanced the rate of electron donation to P700 (+) in the dark. Importantly, neither myxothiazol, an inhibitor of mitochondrial respiration, FCCP, a protonophore, nor propyl gallate, an inhibitor of the plastid terminal oxidase, induced such a strong effect like antimycin A. The results indicate that in the chloroplast of the 137c strain, antimycin A has a site of action outside of the machinery of cyclic electron flow.
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Affiliation(s)
- Taras K Antal
- Biological Faculty, Moscow State University, Vorobyevi Gory, 119992, Moscow, Russia.
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9
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Tikkanen M, Grieco M, Nurmi M, Rantala M, Suorsa M, Aro EM. Regulation of the photosynthetic apparatus under fluctuating growth light. Philos Trans R Soc Lond B Biol Sci 2013; 367:3486-93. [PMID: 23148275 DOI: 10.1098/rstb.2012.0067] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Safe and efficient conversion of solar energy to metabolic energy by plants is based on tightly inter-regulated transfer of excitation energy, electrons and protons in the photosynthetic machinery according to the availability of light energy, as well as the needs and restrictions of metabolism itself. Plants have mechanisms to enhance the capture of energy when light is limited for growth and development. Also, when energy is in excess, the photosynthetic machinery slows down the electron transfer reactions in order to prevent the production of reactive oxygen species and the consequent damage of the photosynthetic machinery. In this opinion paper, we present a partially hypothetical scheme describing how the photosynthetic machinery controls the flow of energy and electrons in order to enable the maintenance of photosynthetic activity in nature under continual fluctuations in white light intensity. We discuss the roles of light-harvesting II protein phosphorylation, thermal dissipation of excess energy and the control of electron transfer by cytochrome b(6)f, and the role of dynamically regulated turnover of photosystem II in the maintenance of the photosynthetic machinery. We present a new hypothesis suggesting that most of the regulation in the thylakoid membrane occurs in order to prevent oxidative damage of photosystem I.
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Affiliation(s)
- Mikko Tikkanen
- Molecular Plant Biology, Department of Biochemistry and Food Chemistry, University of Turku, Turku, Finland
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10
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Pfündel EE, Klughammer C, Meister A, Cerovic ZG. Deriving fluorometer-specific values of relative PSI fluorescence intensity from quenching of F(0) fluorescence in leaves of Arabidopsis thaliana and Zea mays. PHOTOSYNTHESIS RESEARCH 2013; 114:189-206. [PMID: 23196877 DOI: 10.1007/s11120-012-9788-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 11/09/2012] [Indexed: 05/22/2023]
Abstract
The effect of stepwise increments of red light intensities on pulse-amplitude modulated (PAM) chlorophyll (Chl) fluorescence from leaves of A. thaliana and Z. mays was investigated. Minimum and maximum fluorescence were measured before illumination (F(0) and F(M), respectively) and at the end of each light step (F'(0) and F'(M), respectively). Calculated F'(0) values derived from F(0), F(M) and F'(M) fluorescence according to Oxborough and Baker (1997) were lower than the corresponding measured F'(0) values. Based on the concept that calculated F'(0) values are under-estimated because the underlying theory ignores PSI fluorescence, a method was devised to gain relative PSI fluorescence intensities from differences between calculated and measured F'(0). This method yields fluorometer-specific PSI data as its input data (F(0), F(M), F'(0) and F'(M)) depend solely on the spectral properties of the fluorometer used. Under the present conditions, the PSI contribution to F (0) fluorescence was 0.24 in A. thaliana and it was independent on the light acclimation status; the corresponding value was 0.50 in Z. mays. Correction for PSI fluorescence affected Z. mays most: the linear relationship between PSI and PSII photochemical yields was clearly shifted toward the one-to-one proportionality line and maximum electron transport was increased by 50 %. Further, correction for PSI fluorescence increased the PSII reaction center-specific parameter, 1/F(0) - 1/F(M), up to 50 % in A. thaliana and up to 400 % in Z. mays.
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Affiliation(s)
- Erhard E Pfündel
- Lehrstuhl für Botanik II der Universität Würzburg, Julius-von-Sachs Institut für Biowissenschaften, 97082 Würzburg, Germany.
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11
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Grieco M, Tikkanen M, Paakkarinen V, Kangasjärvi S, Aro EM. Steady-state phosphorylation of light-harvesting complex II proteins preserves photosystem I under fluctuating white light. PLANT PHYSIOLOGY 2012; 160:1896-910. [PMID: 23033142 PMCID: PMC3510119 DOI: 10.1104/pp.112.206466] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 09/27/2012] [Indexed: 05/18/2023]
Abstract
According to the "state transitions" theory, the light-harvesting complex II (LHCII) phosphorylation in plant chloroplasts is essential to adjust the relative absorption cross section of photosystem II (PSII) and PSI upon changes in light quality. The role of LHCII phosphorylation upon changes in light intensity is less thoroughly investigated, particularly when changes in light intensity are too fast to allow the phosphorylation/dephosphorylation processes to occur. Here, we demonstrate that the Arabidopsis (Arabidopsis thaliana) stn7 (for state transition7) mutant, devoid of the STN7 kinase and LHCII phosphorylation, shows a growth penalty only under fluctuating white light due to a low amount of PSI. Under constant growth light conditions, stn7 acquires chloroplast redox homeostasis by increasing the relative amount of PSI centers. Thus, in plant chloroplasts, the steady-state LHCII phosphorylation plays a major role in preserving PSI upon rapid fluctuations in white light intensity. Such protection of PSI results from LHCII phosphorylation-dependent equal distribution of excitation energy to both PSII and PSI from the shared LHCII antenna and occurs in cooperation with nonphotochemical quenching and the proton gradient regulation5-dependent control of electron flow, which are likewise strictly regulated by white light intensity. LHCII phosphorylation is concluded to function both as a stabilizer (in time scales of seconds to minutes) and a dynamic regulator (in time scales from tens of minutes to hours and days) of redox homeostasis in chloroplasts, subject to modifications by both environmental and metabolic cues. Exceeding the capacity of LHCII phosphorylation/dephosphorylation to balance the distribution of excitation energy between PSII and PSI results in readjustment of photosystem stoichiometry.
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12
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Nixon PJ, Rich PR. Chlororespiratory Pathways and Their Physiological Significance. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2007. [DOI: 10.1007/978-1-4020-4061-0_12] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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13
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Kruse O, Rupprecht J, Bader KP, Thomas-Hall S, Schenk PM, Finazzi G, Hankamer B. Improved Photobiological H2 Production in Engineered Green Algal Cells. J Biol Chem 2005; 280:34170-7. [PMID: 16100118 DOI: 10.1074/jbc.m503840200] [Citation(s) in RCA: 278] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Oxygenic photosynthetic organisms use solar energy to split water (H2O) into protons (H+), electrons (e-), and oxygen. A select group of photosynthetic microorganisms, including the green alga Chlamydomonas reinhardtii, has evolved the additional ability to redirect the derived H+ and e- to drive hydrogen (H2) production via the chloroplast hydrogenases HydA1 and A2 (H2 ase). This process occurs under anaerobic conditions and provides a biological basis for solar-driven H2 production. However, its relatively poor yield is a major limitation for the economic viability of this process. To improve H2 production in Chlamydomonas, we have developed a new approach to increase H+ and e- supply to the hydrogenases. In a first step, mutants blocked in the state 1 transition were selected. These mutants are inhibited in cyclic e- transfer around photosystem I, eliminating possible competition for e- with H2ase. Selected strains were further screened for increased H2 production rates, leading to the isolation of Stm6. This strain has a modified respiratory metabolism, providing it with two additional important properties as follows: large starch reserves (i.e. enhanced substrate availability), and a low dissolved O2 concentration (40% of the wild type (WT)), resulting in reduced inhibition of H2ase activation. The H2 production rates of Stm6 were 5-13 times that of the control WT strain over a range of conditions (light intensity, culture time, +/- uncoupler). Typically, approximately 540 ml of H2 liter(-1) culture (up to 98% pure) were produced over a 10-14-day period at a maximal rate of 4 ml h(-1) (efficiency = approximately 5 times the WT). Stm6 therefore represents an important step toward the development of future solar-powered H2 production systems.
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Affiliation(s)
- Olaf Kruse
- Department of Biology VIII, Molecular Cell Physiology, University Bielefeld, 33501 Bielefeld, Germany.
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14
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Kramer DM, Roberts AG, Muller F, Cape J, Bowman MK. Q-cycle bypass reactions at the Qo site of the cytochrome bc1 (and related) complexes. Methods Enzymol 2004; 382:21-45. [PMID: 15047094 DOI: 10.1016/s0076-6879(04)82002-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2023]
Affiliation(s)
- David M Kramer
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA
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15
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Forti G, Furia A, Bombelli P, Finazzi G. In vivo changes of the oxidation-reduction state of NADP and of the ATP/ADP cellular ratio linked to the photosynthetic activity in Chlamydomonas reinhardtii. PLANT PHYSIOLOGY 2003; 132:1464-74. [PMID: 12857827 PMCID: PMC167085 DOI: 10.1104/pp.102.018861] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2002] [Revised: 01/15/2003] [Accepted: 01/28/2003] [Indexed: 05/18/2023]
Abstract
The ATP/ADP and NADP/NADPH ratios have been measured in whole-cell extract of the green alga Chlamydomonas reinhardtii, to understand their availability for CO(2) assimilation by the Calvin cycle in vivo. Measurements were performed during the dark-light transition of both aerobic and anaerobic cells, under illumination with saturating or low light intensity. Two different patterns of behavior were observed: (a) In anaerobic cells, during the lag preceding O(2) evolution, ATP was synthesized without changes in the NADP/NADPH ratio, consistently with the operation of cyclic electron flow. (b) In aerobiosis, illumination increased the ATP/ADP ratio independently of the intensity used, whereas the amount of NADPH was decreased at limiting photon flux and regained the dark-adapted level under saturating photon flux. Moreover, under these conditions, the addition of low concentrations of uncouplers stimulated photosynthetic O(2) evolution. These observations suggest that the photosynthetic generation of reducing equivalents rather than the rate of ATP formation limits the photosynthetic assimilation of CO(2) in C. reinhardtii cells. This situation is peculiar to C. reinhardtii, because neither NADPH nor ATP limited this process in plant leaves, as shown by their increase upon illumination in barley (Hordeum vulgare) leaves, independent of light intensity. Experiments are presented and were designed to evaluate the contribution of different physiological processes that might increase the photosynthetic ATP/NADPH ratio-the Mehler reaction, respiratory ATP supply following the transfer of reducing equivalents via the malate/oxaloacetate shuttle, and cyclic electron flow around PSI-to this metabolic situation.
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Affiliation(s)
- Giorgio Forti
- Istituto di Biofisica del Consiglio Nazionale delle Ricerche, Sezione di Milano, Dipartimento di Biologia dell'Università di Milano, Via Celoria 26, Milano 20133, Italy.
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16
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Soriano GM, Guo LW, De Vitry C, Kallas T, Cramer WA. Electron transfer from the Rieske iron-sulfur protein (ISP) to cytochrome f in vitro. Is a guided trajectory of the ISP necessary for competent docking? J Biol Chem 2002; 277:41865-71. [PMID: 12207018 DOI: 10.1074/jbc.m205772200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The time course of electron transfer in vitro between soluble domains of the Rieske iron-sulfur protein (ISP) and cytochrome f subunits of the cytochrome b(6)f complex of oxygenic photosynthesis was measured by stopped-flow mixing. The domains were derived from Chlamydomonas reinhardtii and expressed in Escherichia coli. The expressed 142-residue soluble ISP apoprotein was reconstituted with the [2Fe-2S] cluster. The second-order rate constant, k(2)((ISP-f)) = 1.5 x 10(6) m(-1) s(-1), for ISP to cytochrome f electron transfer was <10(-2) of the rate constant at low ionic strength, k(2)((f-PC))(> 200 x 10(6) m(-1) s(-1)), for the reduction of plastocyanin by cytochrome f, and approximately 1/30 of k(2)((f-PC)) at the ionic strength estimated for the thylakoid interior. In contrast to k(2)((f-PC)), k(2)((ISP-f)) was independent of pH and ionic strength, implying no significant role of electrostatic interactions. Effective pK values of 6.2 and 8.3, respectively, of oxidized and reduced ISP were derived from the pH dependence of the amplitude of cytochrome f reduction. The first-order rate constant, k(1)((ISP-f)), predicted from k(2)((ISP-f)) is approximately 10 and approximately 150 times smaller than the millisecond and microsecond phases of cytochrome f reduction observed in vivo. It is proposed that in the absence of electrostatic guidance, a productive docking geometry for fast electron transfer is imposed by the guided trajectory of the ISP extrinsic domain. The requirement of a specific electrically neutral docking configuration for ISP electron transfer is consistent with structure data for the related cytochrome bc(1) complex.
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Affiliation(s)
- Glenda M Soriano
- Department of Biological Sciences and Program in Biochemistry/Molecular Biology, Purdue University, West Lafayette, Indiana 47907-1392, USA
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17
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Widger W, Cramer W, Hermodson M, Herrmann R. Evidence for a hetero-oligomeric structure of the chloroplast cytochrome b
-559. FEBS Lett 2001. [DOI: 10.1016/0014-5793(85)80005-3] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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18
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Tsujimoto HY, Arnon DI. Differential inhibition by plastoquinone analogues of photoreduction of cytochrome b
-559 in chloroplasts. FEBS Lett 2001. [DOI: 10.1016/0014-5793(85)80189-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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19
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Covián R, Moreno-Sánchez R. Role of protonatable groups of bovine heart bc(1) complex in ubiquinol binding and oxidation. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:5783-90. [PMID: 11722564 DOI: 10.1046/j.0014-2956.2001.02521.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pH dependence of the initial reaction rate catalyzed by the isolated bovine heart ubiquinol-cytochrome c reductase (bc1 complex) varying decylbenzoquinol (DBH) and decylbenzoquinone (DB) concentrations was determined. The affinity for DBH was increased threefold by the protonation of a group with pKa = 5.7 +/- 0.2, while the inhibition constant (Ki) for DB decreased 22 and 2.8 times when groups with pKa = 5.2 +/- 0.6 and 7.7 +/- 0.2, respectively, were protonated. This suggests stabilization of the protonated form of the acidic group by DBH binding. Initial rates were best fitted to a kinetic model involving three protonatable groups. The protonation of the pKa approximately 5.7 group blocked catalysis, indicating its role in proton transfer. The kinetic model assumed that the deprotonation of two groups (pKa values of 7.5 +/- 0.03 and approximately 9.2) decreases the catalytic rate by diminishing the redox potential of the iron-sulfur (Fe-S) cluster. The protonation of the pKa approximately 7.5 group also decreased the reaction rate by 80-86%, suggesting its role as acceptor of a proton from ubiquinol. The lack of effect on the Km for DBH when the pKa 7.5-7.7 group is deprotonated suggests that hydrogen bonding to this residue is not the main factor that determines substrate binding to the Qo site. The possible relationship of the pKa 5.2-5.7 and pKa 7.5-7.7 groups with Glu272 of cytochrome b and His161 of the Fe-S protein is discussed.
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Affiliation(s)
- R Covián
- Departamento de Bioquímica, Instituto Nacional de Cardiología, México.
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de Wolf F, Galmiche J, Kraayenhof R. The antimycin sensitivity of flash-induced ATP synthesis in photosystem I-enriched subchloroplast vesicles. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)81279-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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21
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Finazzi G, Barbagallo RP, Bergo E, Barbato R, Forti G. Photoinhibition of Chlamydomonas reinhardtii in State 1 and State 2: damages to the photosynthetic apparatus under linear and cyclic electron flow. J Biol Chem 2001; 276:22251-7. [PMID: 11294855 DOI: 10.1074/jbc.m011376200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The relationship between state transitions and photoinhibition has been studied in Chlamydomonas reinhardtii cells. In State 2, photosystem II activity was more inhibited by light than in State 1. In State 2, however, the D1 subunit was not degraded, whereas a substantial degradation was observed in State 1. These results suggest that photoinhibition occurs via the generation of an intermediate state in which photosystem II is inactive but the D1 protein is still intact. The accumulation of this state is enhanced in State 2, because in this State only cyclic photosynthetic electron transport is active, whereas there is no electron flow between photosystem II and the cytochrome b(6)f complex (Finazzi, G., Furia, A., Barbagallo, R. P., and Forti, G. (1999) Biochim. Biophys. Acta 1413, 117-129). The activity of photosystem I and of cytochrome b(6)f as well as the coupling of thylakoid membranes was not affected by illumination under the same conditions. This allows repairing the damages to photosystem II thanks to cell capacity to maintain a high rate of ATP synthesis (via photosystem I-driven cyclic electron flow). This capacity might represent an important physiological tool in protecting the photosynthetic apparatus from excess of light as well as from other a-biotic stress conditions.
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Affiliation(s)
- G Finazzi
- Centro di Studio del CNR sulla Biologia Cellulare e Molecolare delle Piante, Via Celoria 26, 20133 Milano, Italy.
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van Voorthuysen T, Dassen HH, Snel JF, Vredenberg WJ. Patch-clamp study on flash-induced secondary electrogenic transport in the thylakoid membrane. Interpretation in terms of a Q-cycle. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1996. [DOI: 10.1016/s0005-2728(96)00100-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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23
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Brandt U. Bifurcated ubihydroquinone oxidation in the cytochrome bc1 complex by proton-gated charge transfer. FEBS Lett 1996; 387:1-6. [PMID: 8654557 DOI: 10.1016/0014-5793(96)00436-x] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The unique bifurcation of electron flow at the ubihydroquinone-oxidation center of the cytochrome bc1 complex is the energy-conserving reaction of the protonmotive Q- cycle and is prerequisite to vectorial proton translocation. The widely accepted Q-cycle reaction scheme describes the overall electron and proton pathways, but does not address the detailed chemistry of this central step. Based on a model of the ubihydroquinone-oxidation pocket containing two ubiquinone molecules in a stacked configuration, a detailed model for the reactions during steady-state catalysis is proposed. In this proton-gated charge-transfer mechanism the reaction is controlled by the deprotonation of the substrate ubihydroquinone.
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Affiliation(s)
- U Brandt
- Universitätsklinikum Frankfurt, Zentrum der Bioligischen Chemie, Frankfurt am Main, Germany.
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Heimann S, Schreiber U. Characterisation of a H2O 2-oxidisable cytochrome b-559 in intact chloroplasts with a new type of LED Array Spectrophotometer. PHOTOSYNTHESIS RESEARCH 1996; 47:187-197. [PMID: 24301826 DOI: 10.1007/bf00016181] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/1995] [Accepted: 12/27/1995] [Indexed: 06/02/2023]
Abstract
Cytochrome (cyt) b-559 absorbance changes in intact chloroplasts were deconvoluted using a previously described LED-Array-Spectrophotometer (Klughammer et al. (1990), Photosynth Res 25: 317-327). When intact chloroplasts were isolated in the presence of ascorbate, approx. 15% of the total cyt b-559 could be transiently oxidised by 200 μM H2O2 in the dark. This fraction displays low-potential properties, as it can be also oxidised by menadione in the presence of 5 mM ascorbate. Heat pretreatment increased the size of this fraction by a factor of 3-4. Low concentrations of cyanide (in the μM range) prolonged the oxidation time while high concentrations suppressed the oxidation (I50=1.5 mM KCN). The former KCN-effect relates to inhibition of ascorbate dependent H2O2-reduction which is catalysed by ascorbate peroxidase, whereas the latter effect reflects competition between H2O2 and CN(-) for the same binding site at the cytochrome heme. In the light, much lower concentrations of H2O2 were required to obtain oxidation, the amplitude depending on light intensity and on the concentration of the added H2O2, but never exceeding approx. 15% of the total cyt b-559. In the light, but not in the dark, H2O2 also induced the transient oxidation of a cyt f fraction similar in size to the H2O2-oxidisable cyt b-559 fraction. In this case, H2O2 serves as an acceptor of Photosystem I in conjunction with the ascorbate peroxidase detoxification system. Light can also induce oxidation of a 15% cyt b-559 fraction without H2O2-addition, if nitrite is present as electron acceptor and the chloroplasts are depleted of ascorbate. It is concluded that light-induced cyt b-559 oxidation in vivo is likely to be restricted to the H2O2-oxidisable cyt b-559 LP fraction and is normally counteracted by ascorbate.
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Affiliation(s)
- S Heimann
- Lehrstuhl Botanik I, Universität Würzburg, Mittlerer Dallenbergweg 64, D-97082, Würzburg, Germany
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Laisk A, Oja V. Coregulation of electron transport through PS I by Cyt b 6 f, excitation capture by P700 and acceptor side reduction. Time kinetics and electron transport requirement. PHOTOSYNTHESIS RESEARCH 1995; 45:11-9. [PMID: 24301375 DOI: 10.1007/bf00032231] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/1994] [Accepted: 05/08/1995] [Indexed: 05/16/2023]
Abstract
Regulation of electron transport rate through Photosystem I (PS I) was investigated in intact sunflower leaves. The rate constant of electron donation via the cytochrome b 6 f complex (kq, s(-1)) was obtained from the postillumination P700(+) reduction rate, measured as the exponential decay of the light-dark difference (D830) of the 830 nm transmission signal. D830 corresponding to maximum oxidisable P700 (D830m) was obtained by applying white light flashes of different intensity and extrapolating the plot of the quantum yield Y vs. D830 to the axis of abscissae (Y->0). Maximum quantum yield of PS I at completely reduced P700 (Ym) was obtained by extrapolating the same plot to the axis of ordinates (D830->0). Regulation of kq, D830m and Ym under rate-limiting CO2 and O2 concentrations applied after air (21% O2, 310 ppm CO2) was investigated. The amplitude of the downregulation of kq (photosynthetic control) was maximal when electron transport rate (ETR) was limited to about 3 nmol cm(-2) s(-1) and decreased when ETR was higher or lower. Downregulation did not occur in the absence of CO2 and O2. These gases acted only as substrates of ribulosebisphosphate carboxylase-oxygenase, no high-affinity reaction of O2 leading to enhanced photosynthetic control (e.g. Mehler reaction) was detected. After the transition, D830m at first decreased and then increased again, showing that the reduction of the PS I acceptor side disappeared as a result of the downregulation of kq. The variation of Ym had two reasons, PS I acceptor side reduction and variable excitation capture efficiency by P700. It is concluded that electron transport through PS I is coregulated by the rate of plastoquinol oxidation at Cyt b 6 f, excitation capture efficiency by P700, and by acceptor side reduction.
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Affiliation(s)
- A Laisk
- Institute of Molecular and Cell Biology, Tartu University, Riia str. 181, EE2400, Tartu, Estonia
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26
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Hope AB, Valente P, Matthews DB. Effects of pH on the kinetics of redox reactions in and around the cytochromebf complex in an isolated system. PHOTOSYNTHESIS RESEARCH 1994; 42:111-20. [PMID: 24306499 DOI: 10.1007/bf02187122] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/1994] [Accepted: 06/21/1994] [Indexed: 05/18/2023]
Abstract
Rate-coefficients describing the electron transfer reactions between P700 and plastocyanin, between cytochromef in cytochromebf complexes and plastocyanin, and between decyl plastoquinol and cytochromebf complexes were determined as a function of pH in the range 4-10 from flash-induced absorbancy changes at four wavelengths. The reactions between P700 and plastocyanin, and between cytochromef and plastocyanin were optimised when there was electrostatic interaction between ionised acidic groups in plastocyanin with a pKa of 4.3-4.7 and ionised basic constituents in P700 (assumed to be in the PSI-F subunit) and in cytochromef, with a pKb of 8.9-9.4. The basic groups are thought to be lysine rather than arginine. This mechanism agrees with that inferred from effects of ionic strength changes on rate-coefficients. The relation between the second-order rate-coefficient for decyl plastoquinol oxidation by thebf complex and pH was characterised by a pKa of 6.1. This is interpreted as showing that the anion radical form of that quinol, which has a pKa of 6, and which becomes progressively protonated when pH is changed from 7 to 5, is essential to reduce cytochromeb-563 (low potential) during quinol oxidation. Above pH 9, permanent effects were observed on this rate-coefficient, which were absent in the reactions between P700, plastocyanin and cytochromef.
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Affiliation(s)
- A B Hope
- School of Biological Sciences, Flinders University, GPO Box 2100, 5001, Adelaide, SA, Australia
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Ananyev G, Renger G, Wacker U, Klimov V. The photoproduction of superoxide radicals and the superoxide dismutase activity of Photosystem II. The possible involvement of cytochrome b559. PHOTOSYNTHESIS RESEARCH 1994; 41:327-38. [PMID: 24310115 DOI: 10.1007/bf00019410] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/1993] [Accepted: 04/11/1994] [Indexed: 05/22/2023]
Abstract
In the present study the light induced formation of superoxide and intrinsic superoxide dismutase (SOD) activity in PS II membrane fragments and D1/D2/Cytb559-complexes from spinach have been analyzed by the use of ferricytochrome c (cyt c(III)) reduction and xanthine/xanthine oxidase as assay systems. The following results were obtained: 1.) Photoreduction of Cyt c (III) by PS II membrane fragments is induced by addition of sodium azide, tetracyane ethylene (TCNE) or carbonylcyanide-p-trifluoromethoxy-phenylhydrazone (FCCP) and after removal of the extrinsic polypeptides by a 1M CaCl2-treatment. This activity which is absent in control samples becomes completely inhibited by the addition of exogenous SOD. 2.) The TCNE induced cyt c(III) photoreduction by PS II membrane fragments was found to be characterized by a half maximal concentration of c1/2=10 μM TCNE. Simultaneously, TCNE inhibits the oxygen evolution rate of PS II membrane fragments with c1/2≈ 3 μM. 3.) The photoproduction of O2 (-) is coupled with H(+)-uptake. This effect is diminished by the addition of the O2 (-)-trap cyt c(III). 4.) D1/D2/Cytb559-complexes and PS II membrane fragments deprived of the extrinsic proteins and manganese exhibit no SOD-activity but are capable of producing O2 (-) in the light if a PS II electron donor is added.Based on these results the site(s) of light induced superoxide formation in PS II is (are) inferred to be located at the acceptor side. A part of the PS II donor side and Cyt b559 in its HP-form are proposed to provide an intrinsic superoxide dismutase (SOD) activity.
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Affiliation(s)
- G Ananyev
- Institut of Soil Science and Photosynthesis, Russian Academy of Sciences, Pushchino, Moskow Region, (Russia)
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Proton-Translocating NAD(P)-H Transhydrogenase and NADH Dehydrogenase in Photosynthetic Membranes. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/s1569-2558(08)60399-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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30
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Laisk A, Oja V. Range of photosynthetic control of postillumination P700(+) reduction rate in sunflower leaves. PHOTOSYNTHESIS RESEARCH 1994; 39:39-50. [PMID: 24310999 DOI: 10.1007/bf00027141] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/1993] [Accepted: 09/29/1993] [Indexed: 05/16/2023]
Abstract
The kinetics of the postillumination reduction of P700(+) which reflects the rate constant for plastoquinol (PQH2) oxidation was recorded in sunflower leaves at different photon absorption densities (PAD), CO2 and O2 concentrations. The P700 oxidation state was calculated from the leaf transmittance at 830 nm logged at 50 μs intervals. The P700(+) dark reduction kinetics were fitted with two exponents with time constants of 6.5 and about 45 ms at atmospheric CO2 and O2 concentrations. The time constant of the fast component, which is the major contributor to the linear electron transport rate (ETR), did not change over the range of PADs of 14.5 to 134 nmol cm(-2) s(-1) in 21% O2, but it increased up to 40 ms under severe limitation of ETR at low O2 and CO2. The acceptor side of Photosystem I (PS I) became reduced in correlation with the downregulation of the PQH2 oxidation rate constant. It is concluded that thylakoid pH-related downregulation of the PQH2 oxidation rate constant (photosynthetic control) is not present under normal atmospheric conditions but appears under severe limitation of the availability of electron acceptors. The measured range of photosynthetic control fits with the maximum variation of ETR under natural stress in C3 plants. Increasing the carboxylase/oxygenase specificity would lead to higher reduction of the PS I acceptor side under stress.
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Affiliation(s)
- A Laisk
- Institute of Molecular and Cell Biology, Tartu University, Riia str. 181, EE2400, Tartu, Estonia
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Manasse RS, Bendall DS. Characteristics of cyclic electron transport in the cyanobacterium Phormidium laminosum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90240-g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Fork DC, Herbert SK. Electron transport and photophosphorylation by Photosystem I in vivo in plants and cyanobacteria. PHOTOSYNTHESIS RESEARCH 1993; 36:149-168. [PMID: 24318920 DOI: 10.1007/bf00033035] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/1992] [Accepted: 02/11/1993] [Indexed: 06/02/2023]
Abstract
Recently, a number of techniques, some of them relatively new and many often used in combination, have given a clearer picture of the dynamic role of electron transport in Photosystem I of photosynthesis and of coupled cyclic photophosphorylation. For example, the photoacoustic technique has detected cyclic electron transport in vivo in all the major algal groups and in leaves of higher plants. Spectroscopic measurements of the Photosystem I reaction center and of the changes in light scattering associated with thylakoid membrane energization also indicate that cyclic photophosphorylation occurs in living plants and cyanobacteria, particularly under stressful conditions.In cyanobacteria, the path of cyclic electron transport has recently been proposed to include an NAD(P)H dehydrogenase, a complex that may also participate in respiratory electron transport. Photosynthesis and respiration may share common electron carriers in eukaryotes also. Chlororespiration, the uptake of O2 in the dark by chloroplasts, is inhibited by excitation of Photosystem I, which diverts electrons away from the chlororespiratory chain into the photosynthetic electron transport chain. Chlororespiration in N-starved Chlamydomonas increases ten fold over that of the control, perhaps because carbohydrates and NAD(P)H are oxidized and ATP produced by this process.The regulation of energy distribution to the photosystems and of cyclic and non-cyclic phosphorylation via state 1 to state 2 transitions may involve the cytochrome b 6-f complex. An increased demand for ATP lowers the transthylakoid pH gradient, activates the b 6-f complex, stimulates phosphorylation of the light-harvesting chlorophyll-protein complex of Photosystem II and decreases energy input to Photosystem II upon induction of state 2. The resulting increase in the absorption by Photosystem I favors cyclic electron flow and ATP production over linear electron flow to NADP and 'poises' the system by slowing down the flow of electrons originating in Photosystem II.Cyclic electron transport may function to prevent photoinhibition to the photosynthetic apparatus as well as to provide ATP. Thus, under high light intensities where CO2 can limit photosynthesis, especially when stomates are closed as a result of water stress, the proton gradient established by coupled cyclic electron transport can prevent over-reduction of the electron transport system by increasing thermal de-excitation in Photosystem II (Weis and Berry 1987). Increased cyclic photophosphorylation may also serve to drive ion uptake in nutrient-deprived cells or ion export in salt-stressed cells.There is evidence in some plants for a specialization of Photosystem I. For example, in the red alga Porphyra about one third of the total Photosystem I units are engaged in linear electron transfer from Photosystem II and the remaining two thirds of the Photosystem I units are specialized for cyclic electron flow. Other organisms show evidence of similar specialization.Improved understanding of the biological role of cyclic photophosphorylation will depend on experiments made on living cells and measurements of cyclic photophosphorylation in vivo.
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Affiliation(s)
- D C Fork
- Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 94305-1297, Stanford, CA, USA
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Cleland RE, Bendall DS. Photosystem I cyclic electron transport: Measurement of ferredoxin-plastoquinone reductase activity. PHOTOSYNTHESIS RESEARCH 1992; 34:409-18. [PMID: 24408836 DOI: 10.1007/bf00029815] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/1992] [Accepted: 06/09/1992] [Indexed: 05/08/2023]
Abstract
Absorbance changes of ferredoxin measured at 463 nm in isolated thylakoids were shown to arise from the activity of the enzyme ferredoxin-plastoquinone reductase (FQR) in cyclic electron transport. Under anaerobic conditions in the presence of DCMU and an appropriate concentration of reduced ferredoxin, a light-induced absorbance decrease due to further reduction of Fd was assigned to the oxidation of the other components in the cyclic pathway, primarily plastoquinone. When the light was turned off, Fd was reoxidised and this gave a direct quantitative measurement of the rate of cyclic electron transport due to the activity of FQR. This activity was sensitive to the classical inhibitor of cyclic electron transport, antimycin, and also to J820 and DBMIB. Antimycin had no effect on Fd reduction although this was inhibited by stigmatellin. This provides further evidence that there is a quinone reduction site outside the cytochrome bf complex. The effect of inhibitors of ferredoxin-NADP(+) reductase and experiments involving the modification of ferredoxin suggest that there may be some role for the reductase as a component of FQR. Contrary to expectations, NADPH2 inhibited FQR activity; ATP and ADP had no effect.
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Affiliation(s)
- R E Cleland
- Department of Biochemistry, University of Cambridge, Tennis Court Road, CB2 1QW, Cambridge, UK
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Samson G, Fork DC. Simultaneous photoreduction and photooxidation of cytochrome b-559 in Photosystem II treated with carbonylcyanide-m-chlorophenylhydrazone. PHOTOSYNTHESIS RESEARCH 1992; 33:203-212. [PMID: 24408664 DOI: 10.1007/bf00030031] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/1991] [Accepted: 04/14/1992] [Indexed: 06/03/2023]
Abstract
The possibility of a Photosystem II (PS II) cyclic electron flow via Cyt b-559 catalyzed by carbonylcyanide m-chlorophenylhydrazone (CCCP) was further examined by studying the effects of the PS II electron acceptor 2,6-dichloro-p-benzoquinone (DCBQ) on the light-induced changes of the redox states of Cyt b-559. Addition to barley thylakoids of micromolar concentrations of DCBQ completely inhibited the changes of the absorbance difference corresponding to the photoreduction of Cyt b-559 observed either in the presence of 10 μM ferricyanide or after Cyt b-559 photooxidation in the presence of 2 μM CCCP. In CCCP-treated thylakoids, the concentration of photooxidized Cyt b-559 decreased as the irradiance of actinic light increased from 2 to 80 W m(-2) but remained close to the maximal concentration (0.53 photooxidized Cyt b-559 per photoactive Photosystem II) in the presence of 50 μM DCBQ. The stimulation of Cyt b-559 photooxidation in parallel with the inhibition of its photoreduction caused by DCBQ demonstrate that the extent of the light-induced changes of the redox state of Cyt b-559 in the presence of CCCP is determined by the difference between the rates of photooxidation and photoreduction of Cyt b-559 occuring simultaneously in a cyclic electron flow around PS II.We also observed that the Photosystem I electron acceptor methyl viologen (MV) at a concentration of 1 mM barely affected the rate and extent of the light-induced redox changes of Cyt b-559 in the presence of either FeCN or CCCP. Under similar experimental conditions, MV strongly quenched Chl-a fluorescence, suggesting that Cyt b-559 is reduced directly on the reducing side of Photosystem II.
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Affiliation(s)
- G Samson
- Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 49305-1297, Stanford, CA, USA
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Ravenel J, Peltier G. Stimulation of the chlororespiratory electron flow by Photosystem II activity in Chlamydomonas reinhardtii. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1992. [DOI: 10.1016/0167-4838(92)90466-q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Oleskin AV, Samullov VD. pH-Abhängigkeit der Cytochromc2 (c)-Reduktion und des Membranpotentials (Δ Ψ) in Modellsystemen und Chromatophoren von Purpurbakterien. J Basic Microbiol 1992. [DOI: 10.1002/jobm.3620320608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Hobbs JD, Wynn M, Nunez DJ, Malkin R, Knaff DB, Ondrias MR. Structural characterization of heme sites in spinach cytochrome b6f complexes: a resonance Raman study. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1059:37-44. [PMID: 1873297 DOI: 10.1016/s0005-2728(05)80185-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Resonance Raman spectra of cytochrome b6f complexes isolated from spinach chloroplasts have been obtained. Selective resonance enhancements and partial reductions of the complex by redox mediators were used to isolate and identify the contributions of heme b6 and heme f sites to the observed spectra. Corresponding spectra for turnip cytochrome f have also been obtained. Power-dependent photoreduction was observed in cytochrome f of the complex as well as in the isolated cytochrome f during the course of the Raman experiments.
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Affiliation(s)
- J D Hobbs
- Department of Chemistry, University of New Mexico, Albuquerque 87131
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38
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Ravenel J, Peltier G. Inhibition of chlororespiration by myxothiazol and antimycin A in Chlamydomonas reinhardtii. PHOTOSYNTHESIS RESEARCH 1991; 28:141-148. [PMID: 24414973 DOI: 10.1007/bf00054127] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/1991] [Accepted: 05/15/1991] [Indexed: 06/03/2023]
Abstract
Myxothiazol and antimycin A are shown to suppress the oxygen transient previously attributed to the flash-induced inhibition of chlororespiration in Chlamydomonas reinhardtii (Peltier et al. 1987, Biochim Biophys Acta 893: 83-90). However, these two compounds do not affect the photosynthetic electron transport chain as inferred by the insensitivity of the CO2-dependent photosynthetic O2 evolution and of the flash-induced electrochromic effect. Chlorophyll fluorescence induction measurements carried out in dark-adapted cells of a mutant of Chlamydomonas lacking photosystem 1, show that myxothiazol and antimycin A significantly increase the redox state of the photosystem 2 acceptors. We conclude from these results that chlororespiration is inhibited by myxothiazol and antimycin A and that the site of inhibition is located on the dark oxidation pathway of the plastoquinone pool. This inhibition is interpreted through the involvement of a myxothiazol and antimycin A sensitive cytochrome in the chlororespiratory chain.
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Affiliation(s)
- J Ravenel
- Département de Physiologie Végétale et Ecosystèmes, Centre d'Etudes de Cadarache, 13108, Saint-Paul-lez-Durance, France
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39
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Rich PR, Madgwick SA, Moss DA. The interactions of duroquinol, DBMIB and NQNO with the chloroplast cytochrome bf complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1991. [DOI: 10.1016/s0005-2728(05)80252-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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40
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Foyer C, Furbank R, Harbinson J, Horton P. The mechanisms contributing to photosynthetic control of electron transport by carbon assimilation in leaves. PHOTOSYNTHESIS RESEARCH 1990; 25:83-100. [PMID: 24420275 DOI: 10.1007/bf00035457] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/1989] [Accepted: 03/07/1990] [Indexed: 05/22/2023]
Abstract
'Photosynthetic control' describes the processes that serve to modify chloroplast membrane reactions in order to co-ordinate the synthesis of ATP and NADPH with the rate at which these metabolites can be used in carbon metabolism. At low irradiance, optimisation of the use of excitation energy is required, while at high irradiance photosynthetic control serves to dissipate excess excitation energy when the potential rate of ATP and NADPH synthesis exceed demand. The balance between ΔpH, ATP synthesis and redox state adjusts supply to demand such that the [ATP]/[ADP] and [NADPH]/[NADP(+)] ratios are remarkably constant in steady-state conditions and modulation of electron transport occurs without extreme fluctuations in these pools.
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Affiliation(s)
- C Foyer
- Laboratoire du Métabolisme, I.N.R.A., Route de St-Cyr, 78000, Versailles, France
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41
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Willey DL, Gray JC. An open reading frame encoding a putative haem-binding polypeptide is cotranscribed with the pea chloroplast gene for apocytochrome f. PLANT MOLECULAR BIOLOGY 1990; 15:347-56. [PMID: 2103453 DOI: 10.1007/bf00036920] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The nucleotide sequence of a 1 kbp region of pea chloroplast DNA upstream from the gene petA encoding apocytochrome f has been determined. An open reading frame of 231 codons (ORF231) encoding a putative membrane-spanning polypeptide is separated by 205 bp from the coding region of petA. The open reading frame is homologous to open reading frames located in a similar position with respect to petA in chloroplast DNA from Marchantia polymorpha, tobacco, rice, wheat and Vicia faba. The sequence around a conserved histidine residue in a putative membrane-spanning region of the polypeptide resembles sequences present in cytochrome b from chromaffin granules and neutrophil membranes, suggesting that the open reading frame may encode a haem-binding polypeptide, possibly a b-type cytochrome. Northern hybridisation analysis indicates the presence in pea chloroplasts of a complex pattern of transcripts containing ORF231. Large transcripts of 5.5 kb, 4.3 kb, 3.4 kb and 2.7 kb encode both ORF231 and apocytochrome f, indicating that ORF231 and petA are co-transcribed.
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Affiliation(s)
- D L Willey
- Botany School, Cambridge Centre for Molecular Recognition, University of Cambridge, UK
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42
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43
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Morand LZ, Frame MK, Colvert KK, Johnson DA, Krogmann DW, Davis DJ. Plastocyanin cytochrome f interaction. Biochemistry 1989; 28:8039-47. [PMID: 2605172 DOI: 10.1021/bi00446a011] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Spinach plastocyanin and turnip cytochrome f have been covalently linked by using a water-soluble carbodiimide to yield an adduct of the two proteins. The redox potential of cytochrome f in the adduct was shifted by -20 mV relative to that of free cytochrome f, while the redox potential of plastocyanin in the adduct was the same as that of free plastocyanin. Solvent perturbation studies showed the degree of heme exposure in the adduct to be less than in free cytochrome f, indicating that plastocyanin was linked in such a way as to bury the exposed heme edge. Small changes were also observed when the resonance Raman spectrum of the adduct was compared to that of free cytochrome f. The adduct was incapable of interacting with or donating electrons to photosystem I. Peptide mapping and sequencing studies revealed two sites of linkage between the two proteins. In one site of linkage, Asp-44 of plastocyanin is covalently linked to Lys-187 of cytochrome f. This represents the first identification of a group on cytochrome f that is involved in the interaction with plastocyanin. The other site of linkage involves Glu-59 and/or Glu-60 of plastocyanin to as yet unidentified amino groups on cytochrome f. Euglena cytochrome c-552 could also be covalently linked to turnip cytochrome f, although with a lower efficiency than spinach plastocyanin. In contrast, a variety of cyanobacterial cytochrome c-553's and a cyanobacterial plastocyanin could not be covalently linked to turnip cytochrome f.
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Affiliation(s)
- L Z Morand
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701
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44
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Willey DL, Gray JC. Two small open reading frames are co-transcribed with the pea chloroplast genes for the polypeptides of cytochrome b-559. Curr Genet 1989; 15:213-20. [PMID: 2766383 DOI: 10.1007/bf00435508] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The genes encoding the 9 kDa and 4 kDa polypeptides of cytochrome b-559 have been located in pea chloroplast DNA by coupled transcription-translation of cloned restriction fragments of chloroplast DNA in a cell-free extract of Escherichia coli and by nucleotide sequence analysis. The genes (psbE and psbF) are located approximately 1.0 kbp downstream of the gene for cytochrome f and are transcribed in the opposite direction, similar to the arrangement in the chloroplast genomes of other higher plants. Nucleotide sequence analysis of this region revealed four open reading frames encoding hydrophobic proteins of 83 (psbE), 39 (psbF), 38 and 40 amino acid residues, which are co-transcribed as a single major RNA of 1.1 kb. The 5' and 3' ends of this RNA have been located by primer extension and S1 nuclease mapping. The 5' end of the RNA is located 140 bp upstream of the initiating ATG codon of psbE and is preceded by typical chloroplast promoter sequences. The 3' end of the RNA is located approximately 515 bp downstream of the TAA stop codon of psbF close to a stable stem-loop structure.
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Affiliation(s)
- D L Willey
- Botany School, University of Cambridge, UK
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45
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de Wolf F, Krab K, Visschers R, de Waard J, Kraayenhof R. Studies on well-coupled Photosystem I-enriched subchloroplast vesicles — characteristics and reinterpretation of single-turnover cyclic electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1988. [DOI: 10.1016/0005-2728(88)90026-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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46
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Davis DJ, Frame MK, Johnson DA. Resonance Raman spectroscopy indicates a lysine as the sixth iron ligand in cytochrome f. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 936:61-6. [PMID: 2846050 DOI: 10.1016/0005-2728(88)90251-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The resonance Raman spectrum of turnip cytochrome f is similar to that of other c-type cytochromes with the exception of a single band at 1532 cm-1 which is shifted to lower frequency relative to its position (1542-1545 cm-1) in other c-type cytochromes. Comparison of the frequency of this band with that in alkylated cytochrome c at high pH suggests that the sixth heme iron ligand in cytochrome f is a deprotonated lysine amino group rather than a methionine sulfur. Comparison of the amino-acid sequences of cytochromes f and c1 suggests lysine-145 as a likely candidate for the sixth heme iron ligand in cytochrome f.
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Affiliation(s)
- D J Davis
- University of Arkansas, Fayetteville, AR 72701
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47
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Wynn RM, Bertsch J, Bruce BD, Malkin R. Green algal cytochrome b6-f complexes: isolation and characterization from Dunaliella saline, Chlamydomonas reinhardtii and Scenedesmus obliquus. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 935:115-22. [PMID: 3415983 DOI: 10.1016/0005-2728(88)90208-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Cytochrome b6-f complexes have been isolated from Chlamydomonas reinhardtii, Dunaliella saline and Scenedesmus obliquus. Each complex is essentially free of chlorophyll and carotenoids and contains cytochrome b6 and cytochrome f hemes in a 2:1 molar ratio. C. reinhardtii and S. obliquus complexes contain the Rieske iron-sulfur protein (present in approx 1:1 molar ratio to cytochrome f) and each catalyzes a DBMIB- and DNP-INT-sensitive electron transfer from duroquinol to spinach plastocyanin. Immunological assays using antibodies to the peptides from the spinach cytochrome complex show varying cross-reactivity patterns except for the complete absence of binding to the Rieske proteins in any of the three complexes, suggesting little structural similarity between the Rieske proteins of algae with those from higher plants. One complex (D. salina) has been uniformly labeled by growth in NaH14CO3 to determine stoichiometries of constituent polypeptide subunits. Results from these studies indicate that all functionally active cytochrome b6-f complexes contain four subunits which occur in equimolar amounts.
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Affiliation(s)
- R M Wynn
- Division of Molecular Plant Biology, University of California, Berkeley 94720
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48
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O'Keefe DP. Structure and function of the chloroplast cytochrome bf complex. PHOTOSYNTHESIS RESEARCH 1988; 17:189-216. [PMID: 24429768 DOI: 10.1007/bf00035448] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/1987] [Accepted: 02/02/1988] [Indexed: 06/03/2023]
Abstract
The chloroplast cytochrome bf complex is an intrinsic multisubunit protein from the thylakoid membrane consisting of four polypeptides: cytochrome f, a two heme containing cytochrome b 6, the Rieske iron-sulfur protein, and a 17 kD polypeptide of undefined function. The complex functions in electron transfer between PSII and PSI, where most mechanisms suggest that the transfer of a single reducing equivalent from plastoquinol to plastocyanin results in the translocation of two protons across the membrane. Primary sequence analyses, dichroism studies, and functional considerations allow the construction of an approximate structural model of a monomeric complex, although some evidence exists for a dimeric structure. Resolution of the properties of the two cytochrome b 6 hemes has relied upon the availability of purified solubilized complex, while evidence in the thylakoid suggests the difference between the two hemes are not as great in situ. Such variability in the spectroscopic and electrochemical properties of the cytochrome b 6 is a major concern during the experimental use of the purified complex. There is a general consensus that the complex contains a plastoquinol oxidizing (Qz) site, although the evidence for a plastoquinone reduction (Qc) site, called for in most mechanistic hypotheses, is less substantive. Probably the most severe challenge to the so called Q-cycle mechanism comes from experimental observations made with cytochrome b 6 initially reduced, where proposed interpretations more closely resemble a b-cycle than a Q-cycle. Although functional during cyclic electron transfer, the role of the complex and its possible interaction with other proteins, has not been completely resolved.
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Affiliation(s)
- D P O'Keefe
- Central Research and Development Department, E.I. duPont de Nemours and Company, Inc. Experimental Station, Bldg. 402, 19898, Wilmington, DE, USA
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49
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Cantrell A, Bryant DA. Nucleotide sequence of the genes encoding cytochrome b-559 from the cyanelle genome of Cyanophora paradoxa. PHOTOSYNTHESIS RESEARCH 1988; 16:65-81. [PMID: 24430992 DOI: 10.1007/bf00039486] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/1987] [Accepted: 12/22/1987] [Indexed: 06/03/2023]
Abstract
Cyanophora paradoxa is a flagellated protozoan which possesses unusual, chloroplast-like organelles referred to as cyanelles. The psbE and psbF genes, which encode the two apoprotein subunits of cytochrome b-559, have been cloned from the cyanelle genome of C. paradoxa. The complete nucleotide sequences of these genes and their flanking sequences were determined by the chain-termination, dideoxy method. The psbE gene is composed of 75 codons and predicts a polypeptide of 8462 Da that is seven to nine residues smaller than most other psbE gene products. The psbF gene consists of 43 codons and predicts a polypeptide of 4761 Da. Two open reading frames, whose sequences are highly conserved among cyanobacteria and numerous higher plants, were located in the nucleotide sequence downstream from the psbF gene. The first open reading frame, denoted psbI, is composed of 39 codons, while the second open reading frame, denoted psbJ, is composed of 41 codons. The predicted amino acid sequences of the psbI and psbJ gene products predict proteins of 5473 and 3973 Da respectively. These proteins are probably integral membrane proteins anchored in the membrane by a single, transmembrane alpha helix. The psbEFIJ genes are probably co-transcribed and constitute an operon as found for other organisms. Each of the four genes is preceded by a polypurine sequence which resembles the consensus ribsosome binding sequences for Escherichia coli.
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Affiliation(s)
- A Cantrell
- Department of Molecular and Cell Biology, Penn State University, S-101 Frear Building, 16802, University Park, PA, USA
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50
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Ortega JM, Hervás M, Losada M. Redox and acid-base characterization of cytochrome b-559 in photosystem II particles. EUROPEAN JOURNAL OF BIOCHEMISTRY 1988; 171:449-55. [PMID: 3278899 DOI: 10.1111/j.1432-1033.1988.tb13810.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The redox and acid/base states and midpoint potentials of cytochrome b-559 have been determined in oxygen-evolving photosystem II (PS II) particles at room temperature in the pH range from 6.5 to 8.5. At pH 7.5 the fresh PS II particles present about 2/3 of their cytochrome b-559 in its reduced and protonated (non-auto-oxidizable) high-potential form and about 1/3 in its oxidized and non-protonated low-potential form. Potentiometric reductive titration shows that the protonated high-potential couple is pH-independent (E'0, + 380 mV), whereas the low-potential couple is non-protonated and pH-independent above pH 7.6 (E'0, pH greater than 7.6, + 140 mV), but becomes pH-dependent below this pH, with a slope of -72 mV/pH unit. Moreover, evidence is presented that in PS II particles cytochrome b-559 can cycle, according to its established redox and acid/base properties, as an energy transducer at two alternate midpoint potentials and at two alternate pKa values. Red light absorbed by PS II induces reduction of cytochrome b-559 in these particles at room temperature, the reaction being completely blocked by dichlorophenyldimethylurea.
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Affiliation(s)
- J M Ortega
- Instituto de Bioquímica Vegetal y Fotosíntesis, Facultad de Biología, Universidad de Sevilla, Spain
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