DOCSLIB.ORG

The Complex Architecture of Oxygenic Photosynthesis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Complex Architecture of Oxygenic Photosynthesis REVIEWS THE COMPLEX ARCHITECTURE OF OXYGENIC PHOTOSYNTHESIS Nathan Nelson and Adam Ben-Shem Abstract | Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on earth. The primary step in this process — the conversion of sunlight into chemical energy — is driven by four, multisubunit, membrane-protein complexes that are known as photosystem I, photosystem II, cytochrome b6f and F-ATPase. Structural insights into these complexes are now providing a framework for the exploration not only of energy and electron transfer, but also of the evolutionary forces that shaped the photosynthetic apparatus. 8,9 PROTONMOTIVE FORCE Oxygenic photosynthesis — the conversion of sunlight After the invention of SDS–PAGE ,the biochemical (pmf). A special case of an into chemical energy by plants, green algae and composition of the four multisubunit protein com- electrochemical potential. It is cyanobacteria — underpins the survival of virtually all plexes began to be elucidated10–14.According to the par- the force that is created by the higher life forms. The production of oxygen and the tial reactions that they catalyse, PSII is defined as a accumulation of protons on one assimilation of carbon dioxide into organic matter water–plastoquinone oxidoreductase, the cytochrome-b f side of a cell membrane. This 6 concentration gradient is determines, to a large extent, the composition of our complex as a plastoquinone–plastocyanin oxidoreduc- generated using energy sources atmosphere and provides all life forms with essential tase, PSI as a plastocyanin–ferredoxin oxidoreductase such as redox potential or ATP. food and fuel. The study of the photosynthetic appara- and the F-ATPase as a pmf-driven ATP synthase15 (FIG. 1). Once established, the pmf can tus is a prime example of research that requires a com- PSI and PSII contain chlorophylls and other pigments be used to carry out work, for example, to synthesize ATP or to bined effort between numerous disciplines, which that harvest light and funnel its energy to a reaction pump compounds across the include quantum mechanics, biophysics, biochemistry, centre. Energy that has been captured by the reaction membrane. molecular and structural biology, as well as physiology centre induces the excitation of specialized reaction- and ecology. The time courses that are measured in centre chlorophylls (PRIMARY ELECTRON DONORS;a special photosynthetic reactions range from femtoseconds to chlorophyll pair in PSI), which initiates the transloca- days, which again highlights the complexity of this tion of an electron across the membrane through a process. chain of cofactors. Water, the electron donor for this Plant photosynthesis is accomplished by a series of process, is oxidized to O2 and 4 protons by PSII. The reactions that occur mainly, but not exclusively, in the electrons that have been extracted from water are shut- chloroplast (BOX 1).Initial biochemical studies showed tled through a quinone pool and the cytochrome-b6 f that the chloroplast thylakoid membrane is capable of complex to plastocyanin, a small, soluble, copper-con- light-dependent water oxidation, NADP reduction and taining protein16.Solar energy that has been absorbed ATP formation1.Biochemical and biophysical studies2–6 by PSI induces the translocation of an electron from Department of revealed that these reactions are catalysed by two sepa- plastocyanin at the inner face of the membrane (thy- Biochemistry, The George S. Wise rate photosystems (PSI and PSII) and an ATP synthase lakoid lumen) to ferredoxin on the opposite side Faculty of Life Sciences, (F-ATPase): the latter produces ATP at the expense of (stroma; FIG. 1). The reduced ferredoxin is subsequently Tel Aviv University, the PROTONMOTIVE FORCE (pmf) that is formed by the light used in numerous regulatory cycles and reactions, Tel Aviv 69978, Israel. reaction.The cytochrome-b f complex mediates elec- which include nitrate assimilation, fatty-acid desatura- Correspondence to N.N. 6 tron transport between PSII and PSI and converts the tion and NADPH production. The CHARGE SEPARATION e-mail: [email protected] redox energy into a high-energy intermediate (pmf) for in PSI and PSII, together with the electron transfer 7 doi:10.1038/nrm1525 ATP formation . through the cytochrome-b6 f complex, leads to the NATURE REVIEWS | MOLECULAR CELL BIOLOGY VOLUME 5 | DECEMBER 2004 | 1 © 2004 Nature Publishing Group REVIEWS unimportant. However, the lost QUANTA can inflict dam- Box 1 | The basic features of higher plant chloroplasts age on the photosynthetic complexes. In the less efficient Chloroplasts (see figure) are Chloroplast PSII, one of the subunits, D1,is turned over so fast that organelles that are bound by a its synthesis represents 50% of the total protein synthesis double membrane and are in chloroplasts, even though D1 actually represents only Stroma lamellae found in the cells of green ~0.1% of the total protein composition of chloro- plants and algae in which Thylakoid plasts21,22.Knowledge of the structures of, and pigment photosynthesis takes place. membranes distributions in, PSI and PSII should eventually help us They contain a third to explain the differences in their quantum yields and membrane system that is Stroma Grana Thylakoid lumen the consequences of these differences. In the following known as thylakoids, where all sections, we review the contribution of recent structural the pigments, electron- Inner membrane data to our understanding of the architecture and func- transport complexes and the Outer membrane tion of oxygenic photosynthesis. ATP synthase (F-ATPase) are located. The thylakoid membranes of higher plants consist of stacks of membranes that form the so-called granal regions.Adjacent grana are connected by non-stacked Photosystem II membranes called stroma lamellae. The fluid compartment that surrounds the thylakoids The PSII reaction centre is composed of two similar is known as the stroma, and the space inside the thylakoids is known as the lumen. ~40-kDa proteins (D1 and D2), which each consist of 5 transmembrane helices, and these proteins coordinate both the manganese cluster of PSII and all of the elec- formation of an ELECTROCHEMICAL-POTENTIAL gradient (the tron-transfer components23 (FIG. 2a).Flanking the reac- pmf), which powers ATP synthesis by the fourth protein tion centre are the intrinsic light-harvesting proteins PRIMARY ELECTRON DONORS 17 complex, F-ATPase .In the dark, CO2 reduction to car- CP43 and CP47,which each consist of 6 transmem- Reaction-centre chlorophyll pairs bohydrates is fuelled by ATP and NADPH18. brane helices and bind 14 and 16 chlorophyll-a mole- (P in PSI and P in PSII) that 700 680 24 are very different from antenna All of the four protein complexes that are necessary cules ,respectively. However, most of the chlorophylls chlorophylls.When they receive for the light-driven reactions of photosynthesis reside in that are associated with PSII are harboured in the light energy (from the antenna the chloroplast, in a membrane continuum of flattened extrinsic, peripheral light-harvesting complex II pigments), they generate a redox- vesicles called thylakoids (FIG. 1a;see also the BOX 1 (LHCII) antenna complexes. These are trimers of the active chemical species. Excited figure). In higher plants, thylakoids are differentiated light-harvesting proteins Lhcb1, Lhcb2 and Lhcb3, P680* donates an electron to another component of PSII, then into two distinct membrane domains — the cylindrical although each trimer can contain different stoichiome- eventually to the cytochrome-b6 f stacked structures known as grana and the intercon- tries of these proteins. The Lhcb proteins have a similar complex and to PSI.After necting single-membrane regions called stroma lamellae. structure, and harbour 12–14 chlorophyll-a and -b mol- donating the electron, P + — the 680 The four membrane complexes that drive the light reac- ecules and up to 4 CAROTENOIDS25,26.The number of strongest oxidant in biology — is tion are not evenly distributed throughout thylakoids: trimers that are associated with PSII varies with irradi- generated. P700* is the strongest + reductant in biology. P700 accepts PSI localizes to the stroma lamellae and is segregated ance level. Energy transfer from LHCII to CP43/CP47 an electron from plastocyanin. from PSII, which is almost exclusively found in the or D1/D2 is mediated by the minor light-harvesting grana; F-ATPase concentrates mainly in the stroma proteins Lhcb6 (CP24), Lhcb5 (CP26) and Lhcb4 CHARGE SEPARATION The process in which excited lamellae, whereas the cytochrome-b6 f complex prefer- (CP29), each of which is similar to an LHCII monomer. entially populates the grana and the grana margins19 The organization of the Lhcb proteins with the PSII P680* and P700* donate their electrons to their respective (FIG. 1a).The recent determination of the structures of reaction centre has been extensively studied using elec- acceptors to generate P + and 680 these complexes — or in the case of F-ATPase, of a close tron microscopy and several low-resolution models P +,respectively. 700 homologue from mitochondria — completes the have been described27,28. ELECTROCHEMICAL POTENTIAL description of the architecture of energy transduction PSII catalyses a unique process of water oxidation and Electrochemical potential is the in oxygenic photosynthesis that has been sought for provides almost all of the earth’s oxygen. Although some sum of the chemical potential the past 50 years (FIG. 1b).Here, we describe
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]
  • Evolution of Photochemical Reaction Centres
    bioRxiv preprint doi: https://doi.org/10.1101/502450; this version posted December 20, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 1 Evolution of photochemical reaction 2 centres: more twists? 3 4 Tanai Cardona, A. William Rutherford 5 Department of Life Sciences, Imperial College London, London, UK 6 Correspondence to: [email protected] 7 8 Abstract 9 The earliest event recorded in the molecular evolution of photosynthesis is the structural and 10 functional specialisation of Type I (ferredoxin-reducing) and Type II (quinone-reducing) reaction 11 centres. Here we point out that the homodimeric Type I reaction centre of Heliobacteria has a Ca2+- 12 binding site with a number of striking parallels to the Mn4CaO5 cluster of cyanobacterial 13 Photosystem II. This structural parallels indicate that water oxidation chemistry originated at the 14 divergence of Type I and Type II reaction centres. We suggests that this divergence was triggered by 15 a structural rearrangement of a core transmembrane helix resulting in a shift of the redox potential 16 of the electron donor side and electron acceptor side at the same time and in the same redox direction. 17 18 Keywords 19 Photosynthesis, Photosystem, Water oxidation, Oxygenic, Anoxygenic, Reaction centre 20 21 Evolution of Photosystem II 22 There is no consensus on when and how oxygenic photosynthesis originated. Both the timing and the 23 evolutionary mechanism are disputed.
    [Show full text]
  • Electron Flow and Management in Living Systems: Advancing Understanding of Electron Transfer to Nitrogenase
    Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 8-2018 Electron Flow and Management in Living Systems: Advancing Understanding of Electron Transfer to Nitrogenase Rhesa N. Ledbetter Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Biochemistry Commons Recommended Citation Ledbetter, Rhesa N., "Electron Flow and Management in Living Systems: Advancing Understanding of Electron Transfer to Nitrogenase" (2018). All Graduate Theses and Dissertations. 7197. https://digitalcommons.usu.edu/etd/7197 This Dissertation is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. ELECTRON FLOW AND MANAGEMENT IN LIVING SYSTEMS: ADVANCING UNDERSTANDING OF ELECTRON TRANSFER TO NITROGENASE by Rhesa N. Ledbetter A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Biochemistry Approved: ______________________ ______________________ Lance C. Seefeldt, Ph.D. Scott A. Ensign, Ph.D. Biochemistry Biochemistry Major Professor Committee Member ______________________ ______________________ Bruce Bugbee, Ph.D. Sean J. Johnson, Ph.D. Plant Physiology Biochemistry Committee Member Committee Member ______________________ ______________________ Nicholas E. Dickenson, Ph.D. Mark R. McLellan, Ph.D. Biochemistry Vice President for Research and Committee Member Dean of the School of Graduate Studies UTAH STATE UNIVERSITY Logan, Utah 2018 ii Copyright © Rhesa N. Ledbetter 2018 All Rights Reserved iii ABSTRACT Electron Flow and Management in Living Systems: Advancing Understanding of Electron Transfer to Nitrogenase by Rhesa N.
    [Show full text]
  • Etude Des Sources De Carbone Et D'énergie Pour La Synthèse Des Lipides De Stockage Chez La Microalgue Verte Modèle Chlamydo
    Aix Marseille Université L'Ecole Doctorale 62 « Sciences de la Vie et de la Santé » Etude des sources de carbone et d’énergie pour la synthèse des lipides de stockage chez la microalgue verte modèle Chlamydomonas reinhardtii Yuanxue LIANG Soutenue publiquement le 17 janvier 2019 pour obtenir le grade de « Docteur en biologie » Jury Professor Claire REMACLE, Université de Liège (Rapporteuse) Dr. David DAUVILLEE, CNRS Lille (Rapporteur) Professor Stefano CAFFARRI, Aix Marseille Université (Examinateur) Dr. Gilles PELTIER, CEA Cadarache (Invité) Dr. Yonghua LI-BEISSON, CEA Cadarache (Directeur de thèse) 1 ACKNOWLEDGEMENTS First and foremost, I would like to express my sincere gratitude to my advisor Dr. Yonghua Li-Beisson for the continuous support during my PhD study and also gave me much help in daily life, for her patience, motivation and immense knowledge. I could not have imagined having a better mentor. I’m also thankful for the opportunity she gave me to conduct my PhD research in an excellent laboratory and in the HelioBiotec platform. I would also like to thank another three important scientists: Dr. Gilles Peltier (co- supervisor), Dr. Fred Beisson and Dr. Pierre Richaud who helped me in various aspects of the project. I’m not only thankful for their insightful comments, suggestion, help and encouragement, but also for the hard question which incented me to widen my research from various perspectives. I would also like to thank collaboration from Fantao, Emmannuelle, Yariv, Saleh, and Alisdair. Fantao taught me how to cultivate and work with Chlamydomonas. Emmannuelle performed bioinformatic analyses. Yariv, Saleh and Alisdair from Potsdam for amino acid analysis.
    [Show full text]
  • Photosynthetic Phosphorylation Above and Below 00C by David 0
    VOL. 48, 1962 BIOCHEMISTRY: HALL AND ARNON 833 10 De Robertis, E., J. Biophy8. Biochem. Cytol., 2, 319 (1956). 11 Eakin, R. M., and J. A. Westfall, ibid., 8, 483 (1960). 12 Eakin, R. M., these PROCEEDINGS, 47, 1084 (1961). 13 Wolken, J. J., in The Structure of the Eye, ed. G. K. Smelser (New York: Academic Press, 1961). 14 Wald, G., ibid. 16 Eakin, R. M., and J. A. Westfall, Embryologia, 6, 84 (1961). 16 Sj6strand, F. S., in The Structure of the Eye, ed. G. K. Smelser (New York: Academic Press, 1961). 17 Miller, W. H., in The Cell, ed. J. Brachet and A. E. Mirsky (New York: Academic Press, 1960), part IV. 18 Miller, W. H., J. Biophys. Biochem. Cytol., 4, 227 (1958). 19 Hesse, R., Z. wiss. Zool., 61, 393 (1896). 20 Bradke, D. L., personal communication. 21 Wolken, J. J., Ann. N. Y. Acad. Sci., 74, 164 (1958). 22 Rohlich, P., and L. J. Torok, Z. wiss. Zool., 54, 362 (1961). 28 Eakin, R. M., and J. A. Westfall, J. Ultrastr. Res. (in press). 24 Franz, V., Jena. Z. Naturwiss., 59, 401 (1923). PHOTOSYNTHETIC PHOSPHORYLATION ABOVE AND BELOW 00C BY DAVID 0. HALL* AND DANIEL I. ARNONt DEPARTMENT OF CELL PHYSIOLOGY, UNIVERSITY OF CALIFORNIA, BERKELEY Read before the Academy, April 25, 1962 CO2 assimilation in photosynthesis consists of a series of dark enzymatic reactions that are driven solely by adenosine triphosphate and reduced pyridine nucleotide. 1-4 The same reactions are now known to operate in nonphotosynthetic cells.5-"3 It follows, therefore, that the distinction between carbon assimilation in photosyn- thetic and nonphotosynthetic cells lies in the manner in which ATP14 and PNH214 are formed.
    [Show full text]
  • Chapter 3 the Title and Subtitle of This Chapter Convey a Dual Meaning
    3.1. Introduction Chapter 3 The title and subtitle of this chapter convey a dual meaning. At first reading, the subtitle Photosynthetic Reaction might seem to indicate that the topic of the structure, function and organization of Centers: photosynthetic reaction centers is So little time, so much to do exceedingly complex and that there is simply insufficient time or space in this brief article to cover the details. While this is John H. Golbeck certainly the case, the subtitle is Department of Biochemistry additionally meant to convey the idea that there is precious little time after the and absorption of a photon to accomplish the Molecular Biology task of preserving the energy in the form of The Pennsylvania State University stable charge separation. University Park, PA 16802 USA The difficulty is there exists a fundamental physical limitation in the amount of time available so that a photochemically induced excited state can be utilized before the energy is invariably wasted. Indeed, the entire design philosophy of biological reaction centers is centered on overcoming this physical, rather than chemical or biological, limitation. In this chapter, I will outline the problem of conserving the free energy of light-induced charge separation by focusing on the following topics: 3.2. Definition of the problem: the need to stabilize a charge-separated state. 3.3. The bacterial reaction center: how the cofactors and proteins cope with this problem in a model system. 3.4. Review of Marcus theory: what governs the rate of electron transfer in proteins? 3.5. Photosystem II: a variation on a theme of the bacterial reaction center.
    [Show full text]
  • Cluster Characterization in Iron-Sulfur Proteins by Magnetic Circular Dichroism (Spectroscopic Probes/Ferredoxins) P
    Proc. Natl. Acad. Sci. USA Vol. 75, No. 11, pp. 5273-5275, November 1978 Biochemistry Cluster characterization in iron-sulfur proteins by magnetic circular dichroism (spectroscopic probes/ferredoxins) P. J. STEPHENS*, A. J. THOMSON*t, T. A. KEIDERLING*t, J. RAWLINGS*§, K. K. RAOT, AND D. 0. HALLS * Department of Chemistry, University of Southern California, Los Angeles, California 90007; and ISchool of Biological Sciences, University of London King's College, 68 Half Moon Lane, London, England Communicated by Martin D. Kamen, August 2,1978- ABSTRACT We report magnetic circular dichroism (MCD) respect to the number of 4-Fe clusters). Ac values are normal- spectra of 4-Fe iron-sulfur clusters in the iron-sulfur proteins ized to a magnetic field of 10 kilogauss. Chromatium high-potential iron protein (HIPIP), Bacillus 1-3 MCD and stearothernophilus ferredoxin and Clostridium pasteurianum Figs. display absorption spectra for clusters ferredoxin. The MCD is found to vary significantly with cluster in the C2-, C3-, and Cl- states, respectively. The absorption oxidation state but is relatively insensitive to the nature of the spectra are typical of 4-Fe clusters, exhibiting few distinct protein. The spectra obtained are compared with the corre- features"l; for a given oxidation state the spectra are insensitive sponding spectra of iron-sulfur proteins containing 2-Fe clus- to the specific protein under study. By comparison, the MCD ters. It is concluded that MCD is useful for the characterization spectra are appreciably more structured than the absorption of iron-sulfur cluster type and oxidation state in iron-sulfur spectra but retain the insensitivity to the nature of the proteins and is superior for this purpose to absorption and nat- associated ural circular dichroism spectroscopy.
    [Show full text]
  • Small One-Helix Proteins Are Essential for Photosynthesis in Arabidopsis
    ORIGINAL RESEARCH Erschienen in: Frontiers in Plant Science ; 8 (2017). - 7 published: 23 January 2017 http://dx.doi.org/10.3389/fpls.2017.00007 doi: 10.3389/fpls.2017.00007 Small One-Helix Proteins Are Essential for Photosynthesis in Arabidopsis Jochen Beck †, Jens N. Lohscheider †, Susanne Albert, Ulrica Andersson, Kurt W. Mendgen, Marc C. Rojas-Stütz, Iwona Adamska and Dietmar Funck * Plant Physiology and Biochemistry Group, Department of Biology, University of Konstanz, Konstanz, Germany The extended superfamily of chlorophyll a/b binding proteins comprises the Light- Harvesting Complex Proteins (LHCs), the Early Light-Induced Proteins (ELIPs) and the Photosystem II Subunit S (PSBS). The proteins of the ELIP family were proposed to function in photoprotection or assembly of thylakoid pigment-protein complexes and are further divided into subgroups with one to three transmembrane helices. Two small One- Helix Proteins (OHPs) are expressed constitutively in green plant tissues and their levels increase in response to light stress. In this study, we show that OHP1 and OHP2 are Edited by: highly conserved in photosynthetic eukaryotes, but have probably evolved independently Peter Jahns, University of Düsseldorf, Germany and have distinct functions in Arabidopsis. Mutations in OHP1 or OHP2 caused severe Reviewed by: growth deficits, reduced pigmentation and disturbed thylakoid architecture. Surprisingly, Wataru Sakamoto, the expression of OHP2 was severely reduced in ohp1 T-DNA insertion mutants and vice Okayama University, Japan versa. In both ohp1 and ohp2 mutants, the levels of numerous photosystem components Rafael Picorel, Spanish National Research Council, were strongly reduced and photosynthetic electron transport was almost undetectable. Spain Accordingly, ohp1 and ohp2 mutants were dependent on external organic carbon *Correspondence: sources for growth and did not produce seeds.
    [Show full text]
  • Electron Transfer Partners of Cytochrome P450
    4 Electron Transfer Partners of Cytochrome P450 Mark J.l. Paine, Nigel S. Scrutton, Andrew W. Munro, Aldo Gutierrez, Gordon C.K. Roberts, and C. Roland Wolf 1. Introduction Although P450 redox partners are usually expressed independently, "self-sufficient" P450 monooxygenase systems have also evolved through Cytochromes P450 contain a heme center the fusion of P450 and CPR genes. These fusion where the activation of molecular oxygen occurs, molecules are found in bacteria and fungi, the best- resulting in the insertion of a single atom of known example being P450 BM3, a fatty acid oxygen into an organic substrate with the con­ (0-2 hydroxylase from Bacillus megaterium, which comitant reduction of the other atom to water. The comprises a soluble P450 with a fiised carboxyl- monooxygenation reaction requires a coupled and terminal CPR module (recently reviewed by stepwise supply of electrons, which are derived Munro^). BM3 has the highest catalytic activity from NAD(P)H and supplied via a redox partner. known for a P450 monooxygenase^ and was for P450s are generally divided into two major classes many years the only naturally occurring ftised sys­ (Class I and Class II) according to the different tem known until the identification of a eukaryotic types of electron transfer systems they use. P450s membrane-bound equivalent fatty acid hydroxy­ in the Class I family include bacterial and mito­ lase, CYP505A1, from the phytopathogenic fungus chondrial P450s, which use a two-component Fusarium oxysporurrP. A number of novel P450 sys­ shuttle system consisting of an iron-sulfur protein tems are starting to emerge from the large numbers (ferredoxin) and ferredoxin reductase (Figure 4.1).
    [Show full text]
  • Biosynthesis of the Chloroplast Cytochrome B6f Complex: Studies In
    The Plant Cell, Vol. 3, 203-212, February 1991 O 1991 American Society of Plant Physiologists Biosynthesis of the Chloroplast Cytochrome bsf Complex: Studies in a Photosynthetic Mutant of Lemna Barry D. Bruce’ and Richard Malkin2 Department of Plant Biology, University of California, Berkeley, Berkeley, California 94720 The biosynthesis of the cytochrome b6f complex has been studied in a mutant, no. 1073, of Lemna perpusilla that contained less than 1% of the four protein subunits when compared with a wild-type strain. RNA gel blot analyses of the mutant indicated that the chloroplast genes for cytochrome f, cytochrome b6, and subunit IV (petA, petB, and petD, respectively) are transcribed and that the petB and petD transcripts undergo their normal processing. Analysis of polysomal polyA+ RNA indicated that the leve1 of translationally active mRNA for the nuclear-encoded Rieske Fe-S protein (petC) was reduced by >lOO-fold in the mutant. lmmunoprecipitation of in vivo labeled proteins indicated that both cytochrome f and subunit IV are synthesized and that subunit IV has a 10-fold higher rate of protein turnover in the mutant. These results are discussed in terms of the assembly of the cytochrome complex and the key role of the Rieske Fe-S protein in this process. INTRODUCTION All organisms capable of photosynthetic autotrophic me- has only started to receive attention. Recent studies have tabolism or heterotrophic respiratory metabolism share the begun to investigate the questions of how these proteins ability to couple electron transport to proton translocation are inserted into a membrane, when and where prosthetic across a membrane.
    [Show full text]
  • Structure of the Lumen-Side Domain of the Chloroplast Rieske Protein Christopher J Carrell, Huamin Zhang, William a Cramer and Janet L Smith*
    Research Article 1613 Biological identity and diversity in photosynthesis and respiration: structure of the lumen-side domain of the chloroplast Rieske protein Christopher J Carrell, Huamin Zhang, William A Cramer and Janet L Smith* Background: The cytochrome b6f complex functions in oxygenic Address: Department of Biological Sciences, photosynthesis as an integral membrane protein complex that mediates coupled Purdue University, West Lafayette, IN 47907-1392, electron transfer and proton translocation. The Rieske [2Fe–2S] protein subunit USA. of the complex functions at the electropositive (p) membrane interface as the *Corresponding author. electron acceptor for plastoquinol and donor for the cytochrome f subunit, and E-mail: [email protected] may have a dynamic role in catalyzing electron and proton transfer at the Key words: membrane interface. There are significant structure/function similarities to the cytochrome b6f complex, cytochrome f, energy transduction, plastoquinone, proton cytochrome bc1 complex of the respiratory chain. translocation Results: The 1.83 Å crystal structure of a 139-residue C-terminal fragment of Received: 19 August 1997 the Rieske [2Fe–2S] protein, derived from the cytochrome b f complex of Revisions requested: 29 September 1997 6 Revisions received: 15 October 1997 spinach chloroplasts, has been solved by multiwavelength anomalous Accepted: 16 October 1997 diffraction. The structure of the fragment comprises two domains: a small ‘cluster-binding’ subdomain and a large subdomain. The [2Fe–2S] cluster- Structure 15 December 1997, 5:1613–1625 binding subdomains of the chloroplast and mitochondrial Rieske proteins are http://biomednet.com/elecref/0969212600501613 virtually identical, whereas the large subdomains are strikingly different despite © Current Biology Ltd ISSN 0969-2126 a common folding topology.
    [Show full text]
  • You Light up My Life
    Chapter 7: Photosynthesis Electromagnetic Spectrum Shortest Gamma rays wavelength X-rays UV radiation Visible light Infrared radiation Microwaves Longest Radio waves wavelength Photons • Packets of light energy • Each type of photon has fixed amount of energy • Photons having most energy travel as shortest wavelength (blue-violet light) Visible Light shortest range of most radiation range of heat escaping longest wavelengths reaching Earth’s surface from Earth’s surface wavelengths (most energetic) (lowest energy) gamma x ultraviolet near-infrared infrared microwaves radio rays rays radiation radiation radiation waves VISIBLE LIGHT 400 450 500 550 600 650 700 Wavelengths of light (nanometers) • Wavelengths humans perceive as different colors • Violet (380 nm) to red (750 nm) • Longer wavelengths, lower energy Fig. 7-2, p.108 Pigments • Colors you can see are the wavelengths not absorbed • These light catching particles capture energy from the various wavelengths. Variety of Pigments Chlorophylls a and b Carotenoids - orange Anthocyanins - purple/red Phycobilins - red Xanthophylls - yellow Chlorophylls chlorophyll a chlorophyll b Wavelength absorption (%) absorption Wavelength Wavelength (nanometers) Accessory Pigments Carotenoids, Phycobilins, Anthocyanins beta-carotene phycoerythrin (a phycobilin) percent of wavelengths absorbed wavelengths (nanometers) Pigments Fig. 7-3a, p.109 Pigments Fig. 7-3b, p.109 Pigments Fig. 7-3c, p.109 Pigments Fig. 7-3d, p.109 http://www.youtube.com/watch?v=fwGcOg PB10o&feature=fvsr Fig. 7-3e, p.109 Pigments Fig. 7-3e, p.109 Pigments in Photosynthesis • Bacteria – Pigments in plasma membranes • Plants – Pigments and proteins organized in chloroplast membranes T.E. Englemann’s Experiment Background • Certain bacterial cells will move toward places where oxygen concentration is high • Photosynthesis produces oxygen T.E.
    [Show full text]