DOCSLIB.ORG

Structure of Photosystem I

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Structure of Photosystem I Biochimica et Biophysica Acta 1507 (2001) 5^31 www.bba-direct.com Review Structure of photosystem I Petra Fromme a;c;*, Patrick Jordan b, Norbert KrauM b;1 a Max Volmer Laboratorium fu«r Biophysikalische Chemie Institut fu«r Chemie, Technische Universita«t Berlin, StraMe des 17 Juni 135, D-10623 Berlin, Germany b Institut fu«r Chemie/Kristallographie, Freie Universita«t Berlin, TakustraMe 6, D-14195 Berlin, Germany c Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA Received 11 December 2000; received in revised form 4 July 2001; accepted 5 July 2001 Abstract In plants and cyanobacteria, the primary step in oxygenic photosynthesis, the light induced charge separation, is driven by two large membrane intrinsic protein complexes, the photosystems I and II. Photosystem I catalyses the light driven electron transfer from plastocyanin/cytochrome c6 on the lumenal side of the membrane to ferredoxin/flavodoxin at the stromal side by a chain of electron carriers. Photosystem I of Synechococcus elongatus consists of 12 protein subunits, 96 chlorophyll a molecules, 22 carotenoids, three [4Fe4S] clusters and two phylloquinones. Furthermore, it has been discovered that four lipids are intrinsic components of photosystem I. Photosystem I exists as a trimer in the native membrane with a molecular mass of 1068 kDa for the whole complex. The X-ray structure of photosystem I at a resolution of 2.5 Aî shows the location of the individual subunits and cofactors and provides new information on the protein^cofactor interactions. [P. Jordan, P. Fromme, H.T. Witt, O. Klukas, W. Saenger, N. KrauM, Nature 411 (2001) 909-917]. In this review, biochemical data and results of biophysical investigations are discussed with respect to the X-ray crystallographic structure in order to give an overview of the structure and function of this large membrane protein. ß 2001 Published by Elsevier Science B.V. Keywords: X-ray crystallography; Photosystem I; Structure; Electron transfer chain; Core antenna; Membrane protein Abbreviations: Chl, chlorophyll; EPR, electron paramagnetic 1. Introduction resonance; ENDOR, electron nuclear double resonance; ETC, electron transfer chain; FNR, ferredoxin-NADP-oxidoreduc- Life on earth depends upon the process of oxy- tase; FX,FA and FB, [4Fe4S] clusters of photosystem I; LHC, genic photosynthesis, using the light energy from light harvesting complex; P700, primary electron donor of PS I; the sun to convert CO2 into carbohydrates. In plants PS I, photosystem I; PS II, photosystem II; A0, spectroscopically and cyanobacteria, the latter producing about 30% identi¢ed primary electron acceptor in PS I; A1, spectroscopically identi¢ed secondary electron acceptor in PS I; RC, reaction of the total oxygen in the atmosphere, two photo- centre; PbRC, purple bacterial photosynthetic reaction centre systems, I and II, catalyse the ¢rst step of this con- * Corresponding author. Fax: +49-30-314-21122. version, the light induced transmembrane charge sep- E-mail addresses: [email protected] aration. In both photosystems, the energy of photons (P. Fromme), [email protected] (N. KrauM). from sun light is used to translocate electrons across 1 Also corresponding author. Present address: Institut fu«r Biochemie, Universita«tsklinikum Charite¨, Medizinische Fakulta«t the thylakoid membrane via a chain of electron car- der Humboldt Universita«t zu Berlin, MonbijoustraMe 2, D-10117 riers. Water, oxidised to O2 and 4H by photosystem Berlin, Germany. Fax +49-30-450-528-942 II, acts as electron donor for the whole process. The 0005-2728 / 01 / $ ^ see front matter ß 2001 Published by Elsevier Science B.V. PII: S0005-2728(01)00195-5 BBABIO 45069 12-10-01 Cyaan Magenta Geel Zwart 6 P. Fromme et al. / Biochimica et Biophysica Acta 1507 (2001) 5^31 Fig. 1. Arrangement of protein subunits and cofactors in one monomeric unit of photosystem I. (a) and (b) View from the stromal side onto the membrane plane along the crystallographic three-fold axis (indicated by a black triangle). The three stromal subunits have been omitted for clarity. Colour coding of the membrane intrinsic subunits is as follows: PsaA, blue; PsaB, red; PsaF, yellow; PsaI, dark pink; PsaJ, green; PsaK, grey; PsaL, brown; PsaM, orange; and PsaX, light pink. In (a) and (b) transmembrane K-helices of the membrane intrinsic subunits are represented as coloured cylinders. (a) Ribbon representation of the extra-membraneous parts of the structure, loops coloured grey. (b) The transmembrane K-helices of the protein and the cofactors of the complex. Transmem- brane K-helices of the subunits PsaF, PsaK and PsaL are labelled according to the nomenclature introduced in Jordan et al. [3]. Transmembrane K-helices of PsaA and PsaB are labelled by single letters, e.g. the blue cylinder `a' represents the transmembrane K-he- lix A-a. Organic cofactors of the ETC are shown in blue, the [4Fe4S] clusters in orange/yellow. Chlorophylls are coloured yellow, ca- rotenoids black and the lipids cyan. two photosystems, which are coupled by a plastoqui- tential drives the synthesis of ATP from ADP and none pool, the cytochrome b6f complex and the solu- inorganic phosphate, catalysed by the ATP-synthase. ble electron carrier proteins plastocyanin or cyto- Finally, photosystem I reduces ferredoxin, providing chrome c6 operate in series. The electron transfer the electrons for the reduction of NADP to processes are coupled to a build up of a di¡erence NADPH by ferredoxin-NADP-oxidoreductase in proton concentration across the thylakoid mem- (FNR). NADPH and ATP are used to reduce CO2 brane. The resulting electrochemical membrane po- to carbohydrates in the subsequent dark reactions. BBABIO 45069 12-10-01 Cyaan Magenta Geel Zwart P. Fromme et al. / Biochimica et Biophysica Acta 1507 (2001) 5^31 7 Fig. 1 (continued). Photosystem I is a large multi-subunit protein tem I is present most dominantly in vivo in trimeric complex, embedded into the photosynthetic thyla- form [4]. A large number of the cofactors present in koid membrane. It catalyses the light induced elec- photosystem I are involved in the processes of light tron transfer from plastocyanin or cytochrome c6 on capturing, charge separation and prevention of pho- the lumenal side of the membrane (inside the thyla- todamage. koids) to ferredoxin or £avodoxin on the stromal The light is captured by a large core antenna sys- side of the membrane. Photosystem I consists of 12 tem consisting of 90 Chla molecules and 22 caroten- (in cyanobacteria), or 13 (in plant systems) individual oids. In plants a membrane integral antenna system proteins. The subunits are named according to their (light harvesting complex (LHCI)) is also closely as- genes PsaA to PsaX (for review on photosystem I see sociated with photosystem I. The excitation energy is [1,2]). Photosystem I from the thermophilic cyano- transferred from the antenna pigments to the pri- bacterium Synechococcus elongatus contains 96 chlo- mary electron donor P700. It was already proposed rophyll (Chl) a molecules, 22 carotenoids, three in the 1960s, that P700 is a dimer of chlorophyll [4Fe4S] clusters and two phylloquinones. In the re- molecules [5,6], and this is con¢rmed by the recent cent X-ray structure at 2.5 Aî resolution [3] four lip- X-ray structure analysis [3]. The excitation energy is ids were also identi¢ed. In cyanobacteria, photosys- used to build up the singlet excited state P700*, lead- BBABIO 45069 12-10-01 Cyaan Magenta Geel Zwart 8 P. Fromme et al. / Biochimica et Biophysica Acta 1507 (2001) 5^31 ing to charge separation, where P700c remains and bacteria. In type I reaction centres, such as the pho- the electron is transferred across the thylakoid mem- tosystem I reaction centre described here, the termi- brane by a chain of electron carriers. This process of nal electron acceptor is an [4Fe4S] cluster (FeS type transmembrane charge separation was intensively in- reaction centre). The photosynthetic reaction centres vestigated spectroscopically (for review on electron of the green sulfur bacteria and the heliobacteria [8,9] transfer in photosystem I see [7]), whereby ¢ve di¡er- are also type I reaction centres. There is structural ent electron acceptors have been identi¢ed: A0 (Chla evidence that all photosynthetic reaction centres have molecule), A1 (phylloquinone), and the three [4Fe4S] evolved from a common ancestor [10], despite the clusters FX,FA and FB. The electron is transferred large di¡erences between photosystems of the same from the terminal FeS cluster to the soluble electron group in structure (for example protein and chromo- carrier ferredoxin. In the case of iron de¢ciency, £a- phore composition), as well as in function (for exam- vodoxin acts as a mobile electron carrier. P700c is ple redox potential, chemical nature of the electron ¢nally rereduced by the soluble electron carrier plas- donor to the reaction centre). tocyanin; in cyanobacteria cytochrome c6 can also In 1993, the ¢rst structural model of photosystem I act as an electron donor to photosystem I. at 6 Aî resolution was published, and later improved Photosystem I belongs to a larger group of pro- to 4 Aî [11^15]. These models provide a ¢rst overview tein^pigment complexes which are able to perform on the structure. Recently, the structure of photosys- light induced charge separation: the photosynthetic tem I was determined at 2.5 Aî resolution [3], provid- reaction centres (RCs). These can be divided into two ing for the ¢rst time detailed insights into the molec- classes de¢ned by the nature of the terminal electron ular architecture of this complex. The structure acceptor. A quinone molecule is the terminal electron contains the models of the protein subunits and the acceptor in type II reaction centres (quinone type 127 cofactors, (96 Chla, 22 carotenoids, two phyllo- reaction centre), which include the photosystem II quinones, three [4Fe4S] clusters and four lipids).
Load more

Recommended publications
  • Light-Induced Psba Translation in Plants Is Triggered by Photosystem II Damage Via an Assembly-Linked Autoregulatory Circuit
    Light-induced psbA translation in plants is triggered by photosystem II damage via an assembly-linked autoregulatory circuit Prakitchai Chotewutmontria and Alice Barkana,1 aInstitute of Molecular Biology, University of Oregon, Eugene, OR 97403 Edited by Krishna K. Niyogi, University of California, Berkeley, CA, and approved July 22, 2020 (received for review April 26, 2020) The D1 reaction center protein of photosystem II (PSII) is subject to mRNA to provide D1 for PSII repair remain obscure (13, 14). light-induced damage. Degradation of damaged D1 and its re- The consensus view in recent years has been that psbA transla- placement by nascent D1 are at the heart of a PSII repair cycle, tion for PSII repair is regulated at the elongation step (7, 15–17), without which photosynthesis is inhibited. In mature plant chloro- a view that arises primarily from experiments with the green alga plasts, light stimulates the recruitment of ribosomes specifically to Chlamydomonas reinhardtii (Chlamydomonas) (18). However, we psbA mRNA to provide nascent D1 for PSII repair and also triggers showed recently that regulated translation initiation makes a a global increase in translation elongation rate. The light-induced large contribution in plants (19). These experiments used ribo- signals that initiate these responses are unclear. We present action some profiling (ribo-seq) to monitor ribosome occupancy on spectrum and genetic data indicating that the light-induced re- cruitment of ribosomes to psbA mRNA is triggered by D1 photo- chloroplast open reading frames (ORFs) in maize and Arabi- damage, whereas the global stimulation of translation elongation dopsis upon shifting seedlings harboring mature chloroplasts is triggered by photosynthetic electron transport.
    [Show full text]
  • Lecture Inhibition of Photosynthesis Inhibition at Photosystem I
    1 Lecture Inhibition of Photosynthesis Inhibition at Photosystem I 1. General Information The popular misconception is that susceptible plants treated with these herbicides “starve to death” because they can no longer photosynthesize. In actuality, the plants die long before the food reserves are depleted. The photosynthetic inhibitors can be divided into two distinct groups, the inhibitors of Photosystem I and inhibitors of Photosystem II. Both of these groups work in the energy production step of photosynthesis, or the light reactions. Light is required as well as photosynthesis for these herbicides to kill susceptible plants. Herbicides that inhibit Photosystem I are considered to be contact herbicides and are often referred to as membrane disruptors. The end result is that cell membranes are rapidly destroyed resulting in leakage of cell contents into the intercellular spaces. These herbicides act as “electron interceptors” or “electron thieves” within Photosystem I of the light reaction of photosynthesis. They divert electrons from the normal electron transport sequence necessary in Photosystem I. This in turn inhibits photosynthesis. The membrane disruption occurs as a result of secondary responses. Herbicides that inhibit Photosystem I are represented by only one family, the bipyridyliums. See chemical structure shown under herbicide families. These molecules are cationic (positively charged) and are therefore highly water soluble. Their cationic properties also make them highly adsorbed to soil colloids resulting in no soil activity. 2. Mode of Action See Figure 7.1 (The electron transport chain in photosynthesis and the sites of action of herbicides that interfere with electron transfer in this chain (Q = electron acceptor; PQ = plastoquinone).
    [Show full text]
  • Photosystem I-Based Applications for the Photo-Catalyzed Production of Hydrogen and Electricity
    University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2014 Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity Rosemary Khuu Le University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Biochemical and Biomolecular Engineering Commons Recommended Citation Le, Rosemary Khuu, "Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity. " PhD diss., University of Tennessee, 2014. https://trace.tennessee.edu/utk_graddiss/3146 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Rosemary Khuu Le entitled "Photosystem I- Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Chemical Engineering. Paul D. Frymier, Major Professor We have read this dissertation and recommend its acceptance: Eric T. Boder, Barry D. Bruce, Hugh M. O'Neill Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Rosemary Khuu Le December 2014 Copyright © 2014 by Rosemary Khuu Le All rights reserved.
    [Show full text]
  • Can Ferredoxin and Ferredoxin NADP(H) Oxidoreductase Determine the Fate of Photosynthetic Electrons?
    Send Orders for Reprints to [email protected] Current Protein and Peptide Science, 2014, 15, 385-393 385 The End of the Line: Can Ferredoxin and Ferredoxin NADP(H) Oxidoreductase Determine the Fate of Photosynthetic Electrons? Tatjana Goss and Guy Hanke* Department of Plant Physiology, Faculty of Biology and Chemistry, University of Osnabrück,11 Barbara Strasse, Osnabrueck, DE-49076, Germany Abstract: At the end of the linear photosynthetic electron transfer (PET) chain, the small soluble protein ferredoxin (Fd) transfers electrons to Fd:NADP(H) oxidoreductase (FNR), which can then reduce NADP+ to support C assimilation. In addition to this linear electron flow (LEF), Fd is also thought to mediate electron flow back to the membrane complexes by different cyclic electron flow (CEF) pathways: either antimycin A sensitive, NAD(P)H complex dependent, or through FNR located at the cytochrome b6f complex. Both Fd and FNR are present in higher plant genomes as multiple gene cop- ies, and it is now known that specific Fd iso-proteins can promote CEF. In addition, FNR iso-proteins vary in their ability to dynamically interact with thylakoid membrane complexes, and it has been suggested that this may also play a role in CEF. We will highlight work on the different Fd-isoproteins and FNR-membrane association found in the bundle sheath (BSC) and mesophyll (MC) cell chloroplasts of the C4 plant maize. These two cell types perform predominantly CEF and LEF, and the properties and activities of Fd and FNR in the BSC and MC are therefore specialized for CEF and LEF re- spectively.
    [Show full text]
  • (CP) Gene of Papaya Ri
    Results and Discussion 4. RESULTS AND DISCUSSION 4.1 Genetic diversity analysis of coat protein (CP) gene of Papaya ringspot virus-P (PRSV-P) isolates from multiple locations of Western India Results – 4.1.1 Sequence analysis In this study, fourteen CP gene sequences of PRSV-P originating from multiple locations of Western Indian States, Gujarat and Maharashtra (Fig. 3.1), have been analyzed and compared with 46 other CP sequences from different geographic locations of America (8), Australia (1), Asia (13) and India (24) (Table 4.1; Fig. 4.1). The CP length of the present isolates varies from 855 to 861 nucleotides encoding 285 to 287 amino acids. Fig. 4.1: Amplification of PRSV-P coat protein (CP) gene from 14 isolates of Western India. From left to right lanes:1: Ladder (1Kb), 2: IN-GU-JN, 3: IN-GU-SU, 4: IN-GU-DS, 5: IN-GU-RM, 6: IN-GU-VL, 7: IN-MH-PN, 8: IN-MH-KO, 9: IN-MH-PL, 10: IN-MH-SN, 11: IN-MH-JL, 12: IN-MH-AM, 13: IN-MH-AM, 14: IN-MH-AK, 15: IN-MH-NS,16: Negative control. Red arrow indicates amplicon of Coat protein (CP) gene. Table 4.1: Sources of coat protein (CP) gene sequences of PRSV-P isolates from India and other countries used in this study. Country Name of Length GenBank Origin¥ Reference isolates* (nts) Acc No IN-GU-JN GU-Jamnagar 861 MG977140 This study IN-GU-SU GU-Surat 855 MG977142 This study IN-GU-DS GU-Desalpur 855 MG977139 This study India IN-GU-RM GU-Ratlam 858 MG977141 This study IN-GU-VL GU-Valsad 855 MG977143 This study IN-MH-PU MH-Pune 861 MH311882 This study Page | 36 Results and Discussion IN-MH-PN MH-Pune
    [Show full text]
  • Glycolysis Citric Acid Cycle Oxidative Phosphorylation Calvin Cycle Light
    Stage 3: RuBP regeneration Glycolysis Ribulose 5- Light-Dependent Reaction (Cytosol) phosphate 3 ATP + C6H12O6 + 2 NAD + 2 ADP + 2 Pi 3 ADP + 3 Pi + + 1 GA3P 6 NADP + H Pi NADPH + ADP + Pi ATP 2 C3H4O3 + 2 NADH + 2 H + 2 ATP + 2 H2O 3 CO2 Stage 1: ATP investment ½ glucose + + Glucose 2 H2O 4H + O2 2H Ferredoxin ATP Glyceraldehyde 3- Ribulose 1,5- Light Light Fx iron-sulfur Sakai-Kawada, F Hexokinase phosphate bisphosphate - 4e + center 2016 ADP Calvin Cycle 2H Stroma Mn-Ca cluster + 6 NADP + Light-Independent Reaction Phylloquinone Glucose 6-phosphate + 6 H + 6 Pi Thylakoid Tyr (Stroma) z Fe-S Cyt f Stage 1: carbon membrane Phosphoglucose 6 NADPH P680 P680* PQH fixation 2 Plastocyanin P700 P700* D-(+)-Glucose isomerase Cyt b6 1,3- Pheophytin PQA PQB Fructose 6-phosphate Bisphosphoglycerate ATP Lumen Phosphofructokinase-1 3-Phosphoglycerate ADP Photosystem II P680 2H+ Photosystem I P700 Stage 2: 3-PGA Photosynthesis Fructose 1,6-bisphosphate reduction 2H+ 6 ADP 6 ATP 6 CO2 + 6 H2O C6H12O6 + 6 O2 H+ + 6 Pi Cytochrome b6f Aldolase Plastoquinol-plastocyanin ATP synthase NADH reductase Triose phosphate + + + CO2 + H NAD + CoA-SH isomerase α-Ketoglutarate + Stage 2: 6-carbonTwo 3- NAD+ NADH + H + CO2 Glyceraldehyde 3-phosphate Dihydroxyacetone phosphate carbons Isocitrate α-Ketoglutarate dehydogenase dehydrogenase Glyceraldehyde + Pi + NAD Isocitrate complex 3-phosphate Succinyl CoA Oxidative Phosphorylation dehydrogenase NADH + H+ Electron Transport Chain GDP + Pi 1,3-Bisphosphoglycerate H+ Succinyl CoA GTP + CoA-SH Aconitase synthetase
    [Show full text]
  • Structure of the Cytochrome B6 F Complex of Oxygenic Photosynthesis
    Structure of the Cytochrome b6 f Complex of Oxygenic Photosynthesis The photosynthetic unit of oxygenic photosynthesis data of 3.0 Å from the complex crystal with another is organized as two large multimolecular membrane analogue inhibitor, TDS, was collected at the SBC complexes, photosystem II (PSII) that extracts low- beamline 19ID, APS. The initial model was developed energy electrons from water and photosystem I (PSI) into a 3.4 Å map of the native complex. Final that raises the energy level of such electrons using refinement was carried out with a dataset from a co- light energy to produce a strong reductant, NADPH. crystal with TDS (Figs. 2, 3). The two photosystems operate in a series linked by a Viewed along the membrane normal, the b6f × third multiprotein complex called the cytochrome b6f complex is 90 Å 55 Å within the membrane side, × complex (Fig.1). The cytochrome b6f complex is a and 120 Å 75 Å on the lumen (p)side (Fig. 2). A membrane-spanning protein complex embedded in prominent feature of this structure is an extended the thylakoid membrane of photosynthetic organisms. quinone exchange cavity between the monomers, The molecular weight of the complex is 220,000 as a which exchanges lipophilic plastoquinone in the dimer with 26 transmembrane helices. The b6f complex bilayer center, and also mediates the electron and controls the electron transfer between the plastoquinol proton transfer across the complex. The heme-binding reduced by PSII and the electron carrier protein 4 transmembrane helices core of the b6f complex plastocyanin that associate with PSI.
    [Show full text]
  • Regulation of Photosynthetic Electron Transport☆
    Biochimica et Biophysica Acta 1807 (2011) 375–383 Contents lists available at ScienceDirect Biochimica et Biophysica Acta journal homepage: www.elsevier.com/locate/bbabio Review Regulation of photosynthetic electron transport☆ Jean-David Rochaix ⁎ Department of Molecular Biology, University of Geneva, Geneva, Switzerland Department of Plant Biology, University of Geneva, Geneva, Switzerland article info abstract Article history: The photosynthetic electron transport chain consists of photosystem II, the cytochrome b6 f complex, Received 14 September 2010 photosystem I, and the free electron carriers plastoquinone and plastocyanin. Light-driven charge separation Received in revised form 11 November 2010 events occur at the level of photosystem II and photosystem I, which are associated at one end of the chain Accepted 13 November 2010 with the oxidation of water followed by electron flow along the electron transport chain and concomitant Available online 29 November 2010 pumping of protons into the thylakoid lumen, which is used by the ATP synthase to generate ATP. At the other end of the chain reducing power is generated, which together with ATP is used for CO assimilation. A Keywords: 2 Electron transport remarkable feature of the photosynthetic apparatus is its ability to adapt to changes in environmental Linear electron flow conditions by sensing light quality and quantity, CO2 levels, temperature, and nutrient availability. These Cyclic electron flow acclimation responses involve a complex signaling network in the chloroplasts comprising the thylakoid Photosystem II protein kinases Stt7/STN7 and Stl1/STN7 and the phosphatase PPH1/TAP38, which play important roles in Photosystem I state transitions and in the regulation of electron flow as well as in thylakoid membrane folding.
    [Show full text]
  • Adjustments of Photosystem Stoichiometry in Chloroplasts
    Proc. Natl. Acad. Sci. USA Vol. 87, pp. 7502-7506, October 1990 Botany Adjustments of photosystem stoichiometry in chloroplasts improve the quantum efficiency of photosynthesis (thylakoids/chloroplast acclimation/reaction center/quantum yield/light quality) WAH SOON CHOW*t, ANASTASIOS MELISt, AND JAN M. ANDERSON* *Commonwealth Scientific and Industrial Organisation, Division of Plant Industry, G.P.O. Box 1600, Canberra, Australian Capital Territory 2601, Australia; and *Department of Plant Biology, University of California, Berkeley, CA 94720 Communicated by Daniel L. Arnon, July 3, 1990 ABSTRACT The efficiency of photosynthetic electron apparatus, given the contrasting light environments in differ- transport depends on the coordinated interaction of photosys- ent plant ecosystems (6-8) and the fact that substantially tem II (PSH) and photosystem I (PSI) in the electron-transport different pigments absorb light for PSI and for PSII in the chain. Each photosystem contains distinct pigment-protein thylakoid membrane of oxygenic photosynthesis. complexes that harvest lightfrom different regions ofthe visible These findings suggested that higher plants and algae spectrum. The light energy is utilized in an endergonic electron- possess regulatory mechanisms that enable chloroplasts to transport reaction at each photosystem. Recent evidence has adjust and optimize the function of the light reactions under shown a large variability in the PSI/PSI stoichiometry in diverse conditions. Recently, evidence in the literature sug- plants grown under different environmental irradiance condi- gested long-term adjustments in photosystem stoichiometry tions. Results in this work are consistent with the notion of a as a plant response to different light-quality conditions during dynamic, rather than static, thylakoid membrane in which the stoichiometry of the two photosystems is adjusted and opti- growth (9, 10).
    [Show full text]
  • Link Between Light and Fatty Acid Synthesis: Thioredoxin-Linked Reductive Activation of Plastidic Acetyl-Coa Carboxylase
    Proc. Natl. Acad. Sci. USA Vol. 94, pp. 11096–11101, September 1997 Plant Biology Link between light and fatty acid synthesis: Thioredoxin-linked reductive activation of plastidic acetyl-CoA carboxylase (coordination with photosynthesisymalonyl-CoA synthesisypeayredox cascadeysignal transduction) YUKIKO SASAKI*, AKIKO KOZAKI, AND MIKA HATANO† Laboratory of Plant Molecular Biology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-01, Japan Communicated by Bob B. Buchanan, University of California, Berkeley, CA, July 9, 1997 (received for review January 30, 1997) ABSTRACT Fatty acid synthesis in chloroplasts is regu- (10). In the redox cascade, thioredoxin acts as a transducer of lated by light. The synthesis of malonyl-CoA, which is cata- redox potential generated by the light reactions of photosyn- lyzed by acetyl-CoA carboxylase (ACCase) and is the first thesis, providing the chloroplasts with a mechanism to coor- committed step, is modulated by lightydark. Plants have dinate the activity of various components of photosynthesis to ACCase in plastids and the cytosol. To determine the possible the presence or absence of light (5–9). involvement of a redox cascade in lightydark modulation of De novo fatty acid synthesis in chloroplasts increases in the ACCase, the effect of DTT, a known reductant of S-S bonds, light and decreases in the dark. The first committed step of this was examined in vitro for the partially purified ACCase from synthesis, catalyzed by ACCase, is the formation of malonyl- pea plant. Only the plastidic ACCase was activated by DTT. CoA. Isolated chloroplasts incorporate acetate into malonyl- This enzyme was activated in vitro more efficiently by reduced CoA within minutes when exposed to light and the incorpo- thioredoxin, which is a transducer of redox potential during ration decreases when exposure ends (11).
    [Show full text]
  • Hydrogenase and Ferredoxin:NADP -Oxidoreductase (FNR)
    Photosynthetic electron partitioning between [FeFe]- hydrogenase and ferredoxin:NADPþ-oxidoreductase (FNR) enzymes in vitro Iftach Yacobya,1, Sergii Pochekailova, Hila Toporikb, Maria L. Ghirardic, Paul W. Kingc,1, and Shuguang Zhanga,1 aCenter for Biomedical Engineering NE47-379, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307; cBiosciences Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401-3305; and bDepartment of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel Edited by Alan R. Fersht, Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom, and approved April 28, 2011 (receivedfor review March 5, 2011) Photosynthetic water splitting, coupled to hydrogenase-catalyzed hydrogen production, is considered a promising clean, renewable source of energy. It is widely accepted that the oxygen sensitivity of hydrogen production, combined with competition between hydrogenases and NADPH-dependent carbon dioxide fixation are the main limitations for its commercialization. Here we provide evi- dence that, under the anaerobic conditions that support hydrogen production, there is a significant loss of photosynthetic electrons toward NADPH production in vitro. To elucidate the basis for com- petition, we bioengineered a ferredoxin-hydrogenase fusion and characterized hydrogen production kinetics in the presence of Fd, ferredoxin:NADPþ-oxidoreductase (FNR), and NADPþ. Replacing the hydrogenase with a ferredoxin-hydrogenase fusion switched the bias of electron transfer from FNR to hydrogenase and resulted in an increased rate of hydrogen photoproduction. These results suggest a new direction for improvement of biohydrogen produc- tion and a means to further resolve the mechanisms that control partitioning of photosynthetic electron transport.
    [Show full text]
  • BBA - Bioenergetics 1860 (2019) 433–438
    BBA - Bioenergetics 1860 (2019) 433–438 Contents lists available at ScienceDirect BBA - Bioenergetics journal homepage: www.elsevier.com/locate/bbabio Review The mechanism of cyclic electron flow T ⁎ W.J. Nawrockia,b, , B. Bailleula, D. Picotc, P. Cardolb, F. Rappaporta,1, F.-A. Wollmana, P. Joliota a Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P. et M. Curie, 75005 Paris, France b Laboratoire de Génétique et Physiologie des Microalgues, Institut de Botanique, Université de Liège, 4, Chemin de la Vallée, B-4000 Liège, Belgium c Institut de Biologie Physico-Chimique, UMR 7099 CNRS-UPMC, 13 rue P. et M. Curie, 75005 Paris, France ARTICLE INFO ABSTRACT Keywords: Apart from the canonical light-driven linear electron flow (LEF) from water to CO2, numerous regulatory and Photosynthesis alternative electron transfer pathways exist in chloroplasts. One of them is the cyclic electron flow around Biophysics Photosystem I (CEF), contributing to photoprotection of both Photosystem I and II (PSI, PSII) and supplying extra Plastoquinone ATP to fix atmospheric carbon. Nonetheless, CEF remains an enigma in the field of functional photosynthesis as Cytochrome b f 6 we lack understanding of its pathway. Here, we address the discrepancies between functional and genetic/ Photosystem I biochemical data in the literature and formulate novel hypotheses about the pathway and regulation of CEF Cyclic electron flow based on recent structural and kinetic information. 1. Linear and cyclic electron flow kinetic and methodological standpoint in the light of our report that PGRL1 is not directly transferring electrons from Fd to PQ during CEF Photosynthesis consists of a photoinduced linear electron flow [1].
    [Show full text]