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'Photosystem II: the water splitting enzyme of photosynthesis and the origin of oxygen in our atmosphere'. Q Rev Biophys 2016; 49:e14. [PMID: 27659174 DOI: 10.1017/s0033583516000093] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
About 3 billion years ago an enzyme emerged which would dramatically change the chemical composition of our planet and set in motion an unprecedented explosion in biological activity. This enzyme used solar energy to power the thermodynamically and chemically demanding reaction of water splitting. In so doing it provided biology with an unlimited supply of reducing equivalents needed to convert carbon dioxide into the organic molecules of life while at the same time produced oxygen to transform our planetary atmosphere from an anaerobic to an aerobic state. The enzyme which facilitates this reaction and therefore underpins virtually all life on our planet is known as Photosystem II (PSII). It is a pigment-binding, multisubunit protein complex embedded in the lipid environment of the thylakoid membranes of plants, algae and cyanobacteria. Today we have detailed understanding of the structure and functioning of this key and unique enzyme. The journey to this level of knowledge can be traced back to the discovery of oxygen itself in the 18th-century. Since then there has been a sequence of mile stone discoveries which makes a fascinating story, stretching over 200 years. But it is the last few years that have provided the level of detail necessary to reveal the chemistry of water oxidation and O-O bond formation. In particular, the crystal structure of the isolated PSII enzyme has been reported with ever increasing improvement in resolution. Thus the organisational and structural details of its many subunits and cofactors are now well understood. The water splitting site was revealed as a cluster of four Mn ions and a Ca ion surrounded by amino-acid side chains, of which seven provide direct ligands to the metals. The metal cluster is organised as a cubane structure composed of three Mn ions and a Ca2+ linked by oxo-bonds with the fourth Mn ion attached to the cubane. This structure has now been synthesised in a non-protein environment suggesting that it is a totally inorganic precursor for the evolution of the photosynthetic oxygen-evolving complex. In summary, the overall structure of the catalytic site has given a framework on which to build a mechanistic scheme for photosynthetic dioxygen generation and at the same time provide a blue-print and incentive to develop catalysts for artificial photo-electrochemical systems to split water and generate renewable solar fuels.
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Herbicides: History, Classification and Genetic Manipulation of Plants for Herbicide Resistance. SUSTAINABLE AGRICULTURE REVIEWS 2015. [DOI: 10.1007/978-3-319-09132-7_3] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Barber J. Photosystem II: Its function, structure, and implications for artificial photosynthesis. BIOCHEMISTRY (MOSCOW) 2014; 79:185-96. [DOI: 10.1134/s0006297914030031] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
The oxygen in the atmosphere is derived from light-driven oxidation of water at a catalytic centre contained within a multi-subunit enzyme known as photosystem II (PSII). PSII is located in the photosynthetic membranes of plants, algae and cyanobacteria and its oxygen-evolving centre (OEC) consists of four manganese ions and a calcium ion surrounded by a highly conserved protein environment. Recently, the structure of PSII was elucidated by X-ray crystallography thus revealing details of the molecular architecture of the OEC. This structural information, coupled with an extensive knowledge base derived from a wide range of biophysical, biochemical and molecular biological studies, has provided a framework for understanding the chemistry of photosynthetic oxygen generation as well as opening up debate about its evolutionary origin.
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Abstract
The oxygen in our atmosphere is derived from and maintained by the water-splitting process of photosynthesis. The enzyme that facilitates this reaction and therefore underpins virtually all life on our planet is known as photosystem II (PSII). It is a multisubunit enzyme embedded in the lipid environment of the thylakoid membranes of plants, algae, and cyanobacteria. Powered by light, PSII catalyzes the chemically and thermodynamically demanding reaction of water splitting. In so doing, it releases molecular oxygen into the atmosphere and provides the reducing equivalents required for the conversion of carbon dioxide into the organic molecules of life. Recently, a fully refined structure of an isolated 700 kDa cyanobacterial dimeric PSII complex was elucidated by X-ray crystallography, which gave organizational and structural details of the 19 subunits (16 intrinsic and 3 extrinsic) that make up each monomer and provided information about the position and protein environments of the many different cofactors it binds. The water-splitting site was revealed as a cluster of four Mn ions and a Ca ion surrounded by amino acid side chains, of which six or seven form direct ligands to the metals. The metal cluster was originally modeled as a cubane-like structure composed of three Mn ions and the Ca (2+) linked by oxo bonds and the fourth Mn attached to the cubane via one of its O atoms. New data from X-ray diffraction and X-ray spectroscopy suggest some alternative arrangements. Nevertheless, all of the models are sufficiently similar to provide a basis for discussing the chemistry by which PSII splits water and makes oxygen.
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Affiliation(s)
- James Barber
- Division of Molecular Biosciences, Faculty of Natural Sciences, Imperial College London, London, UK.
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Abstract
Photosystem II (PSII) is a multisubunit enzyme embedded in the lipid environment of the thylakoid membranes of plants, algae and cyanobacteria. Powered by light, this enzyme catalyses the chemically and thermodynamically demanding reaction of water splitting. In so doing, it releases dioxygen into the atmosphere and provides the reducing equivalents required for the conversion of CO2 into the organic molecules of life. Recently, a fully refined structure of a 700 kDa cyanobacterial dimeric PSII complex was elucidated by X-ray crystallography which gave organizational and structural details of the 19 subunits (16 intrinsic and three extrinsic) which make up each monomer and provided information about the position and protein environments of 57 different cofactors. The water-splitting site was revealed as a cluster of four Mn ions and a Ca2+ ion surrounded by amino acid side chains, of which six or seven form direct ligands to the metals. The metal cluster was modelled as a cubane-like structure composed of three Mn ions and the Ca2+ linked by oxo-bonds with the fourth Mn attached to the cubane via one of its oxygens. The overall structure of the catalytic site is providing a framework to develop a mechanistic scheme for the water-splitting process, knowledge which could have significant implications for mimicking the reaction in an artificial chemical system.
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Affiliation(s)
- J Barber
- Division of Molecular Biosciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK.
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Raval MK, Biswal B, Biswal UC. The mystery of oxygen evolution: analysis of structure and function of photosystem II, the water-plastoquinone oxido-reductase. PHOTOSYNTHESIS RESEARCH 2005; 85:267-93. [PMID: 16170631 DOI: 10.1007/s11120-005-8163-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Accepted: 05/26/2005] [Indexed: 05/04/2023]
Abstract
Photosystem II (PS II) of thylakoid membrane of photosynthetic organisms has drawn attention of researchers over the years because it is the only system on Earth that provides us with oxygen that we breathe. In the recent past, structure of PS II has been the focus of research in plant science. The report of X-ray crystallographic structure of PS II complex by the research groups of James Barber and So Iwata in UK is a milestone in the area of research in photosynthesis. It follows the pioneering and elegant work from the laboratories of Horst Witt and W. Saenger in Germany, and J. Shen in Japan. It is time to analyze the historic events during the long journey made by the researchers to arrive at this point. This review makes an attempt to critically review the growth of the advancement of concepts and knowledge on the photosystem in the background of technological development. We conclude the review with perspectives on research and technology that should reveal the complete story of PS II of thylakoid in the future.
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Affiliation(s)
- M K Raval
- P.G. Department of Chemistry, Government College, Sundargarh, Orissa, India.
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Jones R. The ecotoxicological effects of Photosystem II herbicides on corals. MARINE POLLUTION BULLETIN 2005; 51:495-506. [PMID: 16054161 DOI: 10.1016/j.marpolbul.2005.06.027] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The recent discovery of contamination of the tropical marine environment by Photosystem II (PSII) herbicides used in agriculture and antifouling paints has led to concerns regarding the effects on corals and their symbiotic dinoflagellate algae. In reviewing the ecotoxicological studies conducted so far, PSII herbicides appear able to readily penetrate the coral tissues and rapidly (within minutes) reduce the photochemical efficiency of the intracellular algal symbionts. The dinoflagellates appear at least as sensitive to PSII herbicides as other phototrophs tested so far, with photosynthesis being affected at exceptionally low concentrations (i.e. in the ngl(-1) range). At these levels and over short exposure periods, the effects can be fully reversible (i.e. when corals are returned to clean seawater) and vary according to type of herbicide; however, when exposed to higher concentrations in the light or over longer exposure periods, it results in a long-term sustained reduction of the photochemical efficiency of the algae (symptomatic of chronic photoinhibition). This can result in the dissociation of the symbiosis (bleaching) which is a common but nevertheless significant sub lethal stress response requiring many months to recover from. It is argued that the reliance of corals on an endosymbiotic photoautotrophic energy source, together with predilection for the symbiosis to dissociate when photosynthesis of the algae is affected, renders coral particularly susceptible to changes in environmental conditions-and especially phytotoxins such as PSII herbicides.
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Affiliation(s)
- Ross Jones
- Centre for Marine Studies, Seddon Building (No 82C), St. Lucia Campus, The University of Queensland, Brisbane, QLD 4072, Australia.
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Barber J. Water, water everywhere, and its remarkable chemistry. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1655:123-32. [PMID: 15100024 DOI: 10.1016/j.bbabio.2003.10.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2003] [Revised: 10/30/2003] [Accepted: 10/30/2003] [Indexed: 11/18/2022]
Abstract
Photosystem II (PSII), the multisubunit pigment-protein complex localised in the thylakoid membranes of oxygenic photosynthetic organisms, uses light energy to drive a series of remarkable reactions leading to the oxidation of water. The products of this oxidation are dioxygen, which is released to the atmosphere, and reducing equivalents destined to reduce carbon dioxide to organic molecules. The water oxidation occurs at catalytic sites composed of four manganese atoms (Mn(4)-cluster) and powered by the redox potential of an oxidised chlorophyll a molecule (P680(*+)). Gerald T (Jerry) Babcock and colleagues showed that electron/proton transfer processes from substrate water to P680(*+) involved a tyrosine residue (Y(Z)) and proposed an attractive reaction mechanism for the direct involvement of Y(Z) in the chemistry of water oxidation. The 'hydrogen-atom abstract/metalloradical' mechanism he formulated is an expression of his genius and a highlight of his many other outstanding contributions to photosynthesis research. A structural basis for Jerry's model is now being revealed by X-ray crystallography.
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Affiliation(s)
- Jim Barber
- Department of Biological Sciences, Wolfson Laboratories, Biochemistry Building, South Kensington Campus, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
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Wakeham MC, Frolov D, Fyfe PK, van Grondelle R, Jones MR. Acquisition of photosynthetic capacity by a reaction centre that lacks the QA ubiquinone; possible insights into the evolution of reaction centres? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2003; 1607:53-63. [PMID: 14556913 DOI: 10.1016/j.bbabio.2003.08.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A photosynthetically impaired strain of Rhodobacter sphaeroides containing reaction centres with an alanine to tryptophan mutation at residue 260 of the M-polypeptide (AM260W) was incubated under photosynthetic growth conditions. This incubation produced photosynthetically competent strains containing suppressor mutations that changed residue M260 to glycine or cysteine. Spectroscopic analysis demonstrated that the loss of the Q(A) ubiquinone seen in the original AM260W mutant was reversed in the suppressor mutants. In the mutant where Trp M260 was replaced by Cys, the rate of reduction of the Q(A) ubiquinone by the adjacent (H(A)) bacteriopheophytin was reduced by three-fold. The findings of the experiment are discussed in light of the X-ray crystal structures of the wild-type and AM260W reaction centres, and the possible implications for the evolution of reaction centres as bioenergetic complexes are considered.
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Affiliation(s)
- Marion C Wakeham
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, BS8 1TD Bristol, UK
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Barber J, Nield J. Organization of transmembrane helices in photosystem II: comparison of plants and cyanobacteria. Philos Trans R Soc Lond B Biol Sci 2002; 357:1329-35; discussion 1335, 1367. [PMID: 12437871 PMCID: PMC1693040 DOI: 10.1098/rstb.2002.1132] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Electron microscopy and X-ray crystallography are revealing the structure of photosystem II. Electron crystallography has yielded a 3D structure at sufficient resolution to identify subunit positioning and transmembrane organization of the reaction-centre core complex of spinach. Single-particle analyses are providing 3D structures of photosystem II-light-harvesting complex II supercomplexes that can be used to incorporate high-resolution structural data emerging from electron and X-ray crystallography. The positions of the chlorins and metal centres within photosystem II are now available. It can be concluded that photosystem II is a dimeric complex with the transmembrane helices of CP47/D2 proteins related to those of the CP43/D1 proteins by a twofold axis within each monomer. Further, both electron microscopy and X-ray analyses show that P(680) is not a 'special pair' and that cytochrome b559 is located on the D2 side of the reaction centres some distance from P(680). However, although comparison of the electron microscopy and X-ray models for spinach and Synechococcus elongatus show considerable similarities, there seem to be differences in the number and positioning of some small subunits.
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Affiliation(s)
- J Barber
- Department of Biological Sciences, Wolfson Laboratories, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK.
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Abstract
A structure of photosystem II recently determined by X-ray crystallography at 3.8 A resolution complements structural studies using high-resolution electron microscopy and represents a major step towards understanding how photosynthetic organisms use light energy to oxidise water.
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Affiliation(s)
- James Barber
- Wolfson Laboratories, Department of Biological Sciences, Imperial College of Science, Technology & Medicine, London SW7 2AY, UK.
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Heathcote P, Fyfe PK, Jones MR. Reaction centres: the structure and evolution of biological solar power. Trends Biochem Sci 2002; 27:79-87. [PMID: 11852245 DOI: 10.1016/s0968-0004(01)02034-5] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Reaction centres are complexes of pigment and protein that convert the electromagnetic energy of sunlight into chemical potential energy. They are found in plants, algae and a variety of bacterial species, and vary greatly in their composition and complexity. New structural information has highlighted features that are common to the different types of reaction centre and has provided insights into some of the key differences between reaction centres from different sources. New ideas have also emerged on how contemporary reaction centres might have evolved and on the possible origin of the first chlorophyll-protein complexes to harness the power of sunlight.
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Affiliation(s)
- Peter Heathcote
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London, UK E1 4NS
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Mapping of two tyrosine residues involved in the quinone- (QB) binding site of the D-1 reaction center polypeptide of photosystem II. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)80918-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Reconstitution of plastoquinone in the D1/D2/cytochrome b
-559 photosystem II reaction centre complex. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)80356-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Evidence for the photo-induced oxidation of the primary electron donor P680 in the isolated photosystem II reaction centre. FEBS Lett 2001. [DOI: 10.1016/0014-5793(89)80287-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Gounaris K, Chapman DJ, Barber J. The interaction between the 33 kDa manganese-stabilising protein and the D1
/D2
cytochrome b
-559 complex. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)80119-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Telfer A, Barber J, Evans M. Oxidation-reduction potential dependence of reaction centre triplet formation in the isolated D1/D2/cytochromeb-559 photosystem II complex. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)80418-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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19
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Briantais JM, Cornic G, Hodges M. The modification of chlorophyll fluorescence ofChlamydomonas reinhardtiiby photoinhibition and chloramphenicol addition suggests a form of photosystem II less susceptible to degradation. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)80319-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Li H, Sherman LA. A redox-responsive regulator of photosynthesis gene expression in the cyanobacterium Synechocystis sp. Strain PCC 6803. J Bacteriol 2000; 182:4268-77. [PMID: 10894737 PMCID: PMC101939 DOI: 10.1128/jb.182.15.4268-4277.2000] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have identified genes in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 that are involved with redox control of photosynthesis and pigment-related genes. The genes, rppA (sll0797) and rppB (sll0798), represent a two-component regulatory system that controls the synthesis of photosystem II (PSII) and PSI genes, in addition to photopigment-related genes. rppA (regulator of photosynthesis- and photopigment-related gene expression) and rppB exhibit strong sequence similarity to prokaryotic response regulators and histidine kinases, respectively. In the wild type, the steady-state mRNA levels of PSII reaction center genes increased when the plastoquinone (PQ) pool was oxidized and decreased when the PQ pool was reduced, whereas transcription of the PSI reaction center genes was affected in an opposite fashion. Such results suggested that the redox poise of the PQ pool is critical for regulation of the photosystem reaction center genes. In Delta rppA, an insertion mutation of rppA, the PSII gene transcripts were highly up-regulated relative to the wild type under all redox conditions, whereas transcription of phycobilisome-related genes and PSI genes was decreased. The higher transcription of the psbA gene in Delta rppA was manifest by higher translation of the D1 protein and a concomitant increase in O(2) evolution. The results demonstrated that RppA is a regulator of photosynthesis- and photopigment-related gene expression, is involved in the establishment of the appropriate stoichiometry between the photosystems, and can sense changes in the PQ redox poise.
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Affiliation(s)
- H Li
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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Egner U, Gerbling KP, Hoyer GA, Krüger G, Wegner P. Design of Inhibitors of Photosystem II using a Model of the D1 Protein. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1096-9063(199606)47:2<145::aid-ps381>3.0.co;2-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Lancaster CR, Michel H. Refined crystal structures of reaction centres from Rhodopseudomonas viridis in complexes with the herbicide atrazine and two chiral atrazine derivatives also lead to a new model of the bound carotenoid. J Mol Biol 1999; 286:883-98. [PMID: 10024457 DOI: 10.1006/jmbi.1998.2532] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In a reaction of central importance to the energetics of photosynthetic bacteria, light-induced electron transfer in the reaction centre (RC) is coupled with the uptake of protons from the cytoplasm at the binding site of the secondary quinone (QB). It has been established by X-ray crystallography that the triazine herbicide terbutryn binds to the QB site. However, the exact description of protein-triazine interactions has had to await the refinement of higher-resolution structures. In addition, there is also interest in the role of chirality in the activity of herbicides. Here, we report the structural characterisation of triazine binding by crystallographic refinement of complexes of the RC either with the triazine inhibitor atrazine (Protein Data Bank (PDB) entry 5PRC) or with the chiral atrazine derivatives, DG-420314 (S(-) enantiomer, PDB entry 6PRC) or DG-420315 (R(+) enantiomer, PDB entry 7PRC). Due to the high quality of the data collected, it has been possible to describe the exact nature of triazine binding and its effect on the structure of the protein at high-resolution limits of 2.35 A (5PRC), 2.30 A (6PRC), and 2.65 A (7PRC), respectively. In addition to two previously implied hydrogen bonds, a third hydrogen bond, binding the distal side of the inhibitors to the protein, and four additional hydrogen bonds mediated by two tightly bound water molecules on the proximal side of the inhibitors, are apparent. Based on the high quality data collected on the RC complexes of the two chiral atrazine derivatives, unequivocal assignment of the structure at the chiral centres was possible, even though the differences in structures of the substituents are small. The structures provide explanations for the relative binding affinities of the two chiral compounds. Although it was not an explicit goal of this work, the new data were of sufficient quality to improve the original model also regarding the structure of the bound carotenoid 1,2-dihydroneurosporene. A carotenoid model with a cis double bond at the 15,15' position fits the electron density better than the original model with a 13,14-cis double bond.
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Affiliation(s)
- C R Lancaster
- Abteilung Molekulare Membranbiologie, Max-Planck-Institut für Biophysik, Heinrich-Hoffmann-Str. 7, Frankfurt am Main, D-60528, Germany
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Hankamer B, Barber J, Boekema EJ. STRUCTURE AND MEMBRANE ORGANIZATION OF PHOTOSYSTEM II IN GREEN PLANTS. ACTA ACUST UNITED AC 1997; 48:641-671. [PMID: 15012277 DOI: 10.1146/annurev.arplant.48.1.641] [Citation(s) in RCA: 211] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Photosystem II (PSII) is the pigment protein complex embedded in the thylakoid membrane of higher plants, algae, and cyanobacteria that uses solar energy to drive the photosynthetic water-splitting reaction. This chapter reviews the primary, secondary, tertiary, and quaternary structures of PSII as well as the function of its constituent subunits. The understanding of in vivo organization of PSII is based in part on freeze-etched and freeze-fracture images of thylakoid membranes. These images show a resolution of about 40-50 A and so provide information mainly on the localization, heterogeneity, dimensions, and shapes of membrane-embedded PSII complexes. Higher resolution of about 15-40 A has been obtained from single particle images of isolated PSII complexes of defined and differing subunit composition and from electron crystallography of 2-D crystals. Observations are discussed in terms of the oligomeric state and subunit organization of PSII and its antenna components.
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Affiliation(s)
- Ben Hankamer
- Wolfson Laboratories, Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, United Kingdom, Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, Groningen, NL-9747 AG The Netherlands
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Gatzen G, Müller MG, Griebenow K, Holzwarth AR. Primary Processes and Structure of the Photosystem II Reaction Center. 3. Kinetic Analysis of Picosecond Energy Transfer and Charge Separation Processes in the D1−D2−cyt-b559 Complex Measured by Time-Resolved Fluorescence. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp9530865] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Guido Gatzen
- Max-Planck-Institut für Strahlenchemie, Stiftstrasse 34−36, D-45470 Mülheim a.d. Ruhr, Germany
| | - Marc G. Müller
- Max-Planck-Institut für Strahlenchemie, Stiftstrasse 34−36, D-45470 Mülheim a.d. Ruhr, Germany
| | - Kai Griebenow
- Max-Planck-Institut für Strahlenchemie, Stiftstrasse 34−36, D-45470 Mülheim a.d. Ruhr, Germany
| | - Alfred R. Holzwarth
- Max-Planck-Institut für Strahlenchemie, Stiftstrasse 34−36, D-45470 Mülheim a.d. Ruhr, Germany
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Barbato R, Friso G, Ponticos M, Barber J. Characterization of the light-induced cross-linking of the alpha-subunit of cytochrome b559 and the D1 protein in isolated photosystem II reaction centers. J Biol Chem 1995; 270:24032-7. [PMID: 7592601 DOI: 10.1074/jbc.270.41.24032] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Illumination of the isolated reaction center of photosystem II generates a protein of 41 kDa molecular mass. Using immunoblotting, it is confirmed that the protein is an adduct of the D1 protein and the alpha-subunit of cytochrome b559. Its formation seems to be photochemically induced, being independent of temperature between 4 and 20 degrees C and unaffected by a mixture of protease inhibitors. The maximum levels are detected when the pH is in the region 6.5-8.5 and when illumination intensities are moderate. Although higher light intensities induce a higher rate of formation, the accumulation of elevated levels of the 41-kDa protein does not occur due to light-induced degradation. This degradation is also unaffected by the presence of protease inhibitors. Proteolytic mapping and N-terminal sequencing indicates that the cross-linking process involves the N-terminal serine of the alpha-subunit of cytochrome b559 and D1 residues in the 239-244 FGQEEE motif close to the QB binding site. In conclusion, the results indicate that the N terminus of the alpha-subunit is exposed on the stromal side of photosystem II in such a way as to undergo light-induced cross-linking in the QB region of the D1 protein. They also suggest that the 41-kDa adduct may be an intermediate before the light-induced cleavage of the D1 protein in the FGQEEE region.
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Affiliation(s)
- R Barbato
- Biochemistry Department, Wolfson Laboratories, Imperial College of Science, Technology & Medicine, London, United Kingdom
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Molecular Genetic Manipulation and Characterization of Mutant Photosynthetic Reaction Centers from Purple Nonsulfur Bacteria. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/s1569-2558(08)60398-7] [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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Andersson B, Barber J. Composition, Organization, and Dynamics of Thylakoid Membranes. MOLECULAR PROCESSES OF PHOTOSYNTHESIS 1994. [DOI: 10.1016/s1569-2558(08)60394-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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31
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Blankenship RE. Protein structure, electron transfer and evolution of prokaryotic photosynthetic reaction centers. Antonie Van Leeuwenhoek 1994; 65:311-29. [PMID: 7832589 DOI: 10.1007/bf00872216] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Photosynthetic reaction centers from a variety of organisms have been isolated and characterized. The groups of prokaryotic photosynthetic organisms include the purple bacteria, the filamentous green bacteria, the green sulfur bacteria and the heliobacteria as anoxygenic representatives as well as the cyanobacteria and prochlorophytes as oxygenic representatives. This review focuses on structural and functional comparisons of the various groups of photosynthetic reaction centers and considers possible evolutionary scenarios to explain the diversity of existing photosynthetic organisms.
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Affiliation(s)
- R E Blankenship
- Department of Chemistry and Biochemistry, Arizona State University, Tempe 85287-1604
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32
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Durrant JR, Hastings G, Joseph DM, Barber J, Porter G, Klug DR. Rate of oxidation of P680 in isolated photosystem 2 reaction centers monitored by loss of chlorophyll stimulated emission. Biochemistry 1993; 32:8259-67. [PMID: 8347624 DOI: 10.1021/bi00083a029] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We have continued our studies of the primary photochemistry of isolated photosystem 2 reaction centers using femtosecond transient absorption spectroscopy. Experiments were performed over a wide range of excitation and probe wavelengths, using several data collection time scales. This has enabled us to resolve five different lifetimes ranging between 100 fs and 200 ps plus a nanosecond component. We demonstrate here and elsewhere [e.g., Durrant, J.R., Hastings, G., Joseph, D. M., Barber, J., Porter, G., & Klug, D. R. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 11632-11636] that the kinetic spectra associated with all but two of these lifetimes are clearly distinguishable. We have previously reported that a 21-ps lifetime is associated with pheophytin reduction [Hastings, G., Durrant, J. R., Hong, Q., Barber, J., Porter, G., & Klug, D. R. (1992) Biochemistry 31, 7638-7647]. In this paper, we show that it is possible to spectrally and temporally resolve stimulated emission from PS2 reaction centers with great accuracy and that this stimulated emission is largely unaffected by those kinetic components which are faster than 21 ps. The observation of a distinct stimulated emission band allows us to distinguish charge-separated states from chlorin singlet states. In this way, we are able to show that the proportion of charge-separated states prior to the 21-ps component is between 0% and 25%. We also show that the shape of the spectrum which we obtain for the state P680+Ph- is essentially invariant between 100 ps and 9 ns, and is the same as that previously reported for P680+Ph- by other researchers.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J R Durrant
- Department of Biology, Imperial College, London, U.K
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33
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Modeling and energy minimization studies on the herbicide binding protein (D1) in Photosystem II of plants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1993. [DOI: 10.1016/0005-2728(93)90091-s] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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34
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Lers A, Heifetz P, Boynton J, Gillham N, Osmond C. The carboxyl-terminal extension of the D1 protein of photosystem II is not required for optimal photosynthetic performance under CO2- and light-saturated growth conditions. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)37068-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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35
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Hastings G, Durrant JR, Barber J, Porter G, Klug DR. Observation of pheophytin reduction in photosystem two reaction centers using femtosecond transient absorption spectroscopy. Biochemistry 1992; 31:7638-47. [PMID: 1510949 DOI: 10.1021/bi00148a027] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Photosystem two reaction centers have been studied using a sensitive femtosecond transient absorption spectrometer. Measurements were performed at 295 K using different excitation wavelengths and excitation intensities which are shown to avoid multiphoton absorption by the reaction centers. Analyses of results collected over a range of time scales and probe wavelengths allowed the resolution of two exponential components in addition to those previously reported [Durrant, J. R., Hastings, G., Hong, Q., Barber, J., Porter, G., & Klug, D. R. (1992) Chem. Phys. Lett. 188, 54-60], plus the long-lived radical pair itself. A 21-ps component was observed. The process(es) responsible for this component was (were) found to produce bleaching of a pheophytin ground-state absorption band at 545 nm and the simultaneous appearance of a pheophytin anion absorption band at 460 nm resulting in a transient spectrum which was that of the radical pair P680+Ph-. This component is assigned to the production of reduced pheophytin. A lower limit of 60% of the final pheophytin reduction was found to occur at this rate. Despite subtle differences in transient spectra, the lifetime and yield of this pheophytin reduction are essentially independent of excitation wavelength within the signal to noise limitations of these experiments. A long-lived species was also observed. This species is produced by those processes which result in the 21-ps component, and it has a spectrum which is found to be independent of excitation wavelength. This spectrum is characteristic of the primary radical pair state P680+Ph-. In addition, a 200-ps component was found which is tentatively assigned to a slow energy-transfer/trapping process. This component was absent if P680 was excited directly and is therefore not integral to primary radical pair formation. Overall, it is concluded that the rate of pheophytin reduction is limited to (21 ps)-1, even when P680 is directly excited.
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Affiliation(s)
- G Hastings
- Department of Biology, Imperial College, London, United Kingdom
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36
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Kodera Y, Takura K, Kawamori A. Distance of P680 from the manganese complex in Photosystem II studied by time resolved EPR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1992. [DOI: 10.1016/0167-4838(92)90462-m] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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37
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De Las Rivas J, Andersson B, Barber J. Two sites of primary degradation of the D1-protein induced by acceptor or donor side photo-inhibition in photosystem II core complexes. FEBS Lett 1992; 301:246-52. [PMID: 1577160 DOI: 10.1016/0014-5793(92)80250-k] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Depending on experimental conditions we have found that photo-inhibitory treatment of photosystem II (PSII) core complexes, isolated from wheat, can generate two fragments of about 23-24 kDa that contain either the C-terminal or N-terminal regions of the D1-protein. A 24 kDa C-terminal fragment appears when the water splitting reaction is not functional and an electron acceptor is present. This 'donor'-side inhibition also generates an N-terminal fragment of about 10 kDa and is suggested to be due to the cleavage of a peptide bond in the region connecting transmembrane segments I and II of the D1-protein. In contrast, an N-terminal 23 kDa D1-protein fragment is detected when the water splitting reactions of the isolated complex are active, and occurs in the absence of an added electron acceptor. This 'acceptor'-side photo-inhibition also generates a C-terminal fragment of about 10 kDa.
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Affiliation(s)
- J De Las Rivas
- Biochemistry Department, Wolfson Laboratories, Imperial College of Science, Technology and Medicine, London, UK
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38
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Abstract
The ureas and phenolics are two major classes of herbicides that act on Photosystem II (PSII) and are normally inactive in the photosynthetic reaction centers of purple bacteria. However, the triazine-resistant mutant T4 from Rhodopseudomonas (Rps.) viridis, which has the tyrosine residue at position 222 on the L subunit substituted for phenylalanine (TyrL222Phe), is sensitive to both ureas and phenolics. Since for the first time structural data on urea binding are available, T4 is a particularly interesting model for the herbicide-binding site of PSII.
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Affiliation(s)
- I Sinning
- Department of Molecular Biology, University of Uppsala, Sweden
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39
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Bustos SA, Golden SS. Light-regulated expression of the psbD gene family in Synecbococcus sp. strain PCC 7942: evidence for the role of duplicated psbD genes in cyanobacteria. ACTA ACUST UNITED AC 1992; 232:221-30. [PMID: 1372952 DOI: 10.1007/bf00280000] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The genome of the cyanobacterium Synechococcus sp. strain PCC 7942 contains two psbD genes encoding the D2 protein of the photosystem II reaction center: psbDI, which is cotranscribed as a discistronic message with psbC (the gene encoding CP43, a chlorophyll-a binding protein), and psbDII, which is monocistronic. Northern blot analysis of psbD transcripts showed that the two genes responded differently when wild-type cells were shifted from moderate to high light intensity. Whereas psbDII transcripts increased 500% relative to unshifted control cells, psbDI-psbC transcripts remained unchanged. The beta-galactosidase activities expressed from translational fusions between the psbD genes and the Escherichia coli lacZ reporter gene displayed responses similar to those seen in the RNA. D2 protein levels in thylakoid membranes from wild-type cells increased to 250% of those of the unshifted control cells 12 h after a shift to high light intensities. In contrast, in a mutant strain (AMC016) that carries an inactive psbDII gene, D2 levels decreased by 50% under identical conditions. These results suggested that induction of psbDII gene expression by light can serve as a supplementary system for maintaining a functional photosystem II reaction center at high light intensity. This hypothesis was corroborated by mixed-culture experiments, in which AMC016 cells competed poorly with wild-type cells at high light intensity. These data suggest for the first time that differential expression of members of a cyanobacterial gene family serves to maintain a functional PSII reaction center under diverse environmental conditions.
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Affiliation(s)
- S A Bustos
- Department of Biology, Texas A & M University, College Station 77843
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40
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Abstract
Even though light is the ultimate substrate for photosynthetic energy conversion, it can also harm plants. This toxicity is targeted to the water-splitting photosystem II and leads to damage and degradation of the reaction centre D1-polypeptide. The degradation of this very important protein appears to be a direct consequence of photosystem II chemistry involving highly oxidizing radicals and toxic oxygen species. The frequency of this damage is relatively low under normal conditions but becomes a significant problem for the plant with increasing light intensity, especially when combined with other environmental stress factors. However, the plant survives this photoinhibition through an efficient repair system which involves an autoproteolytic activity of the photosystem II complex, D1-polypeptide synthesis and reassembly of active complexes.
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Affiliation(s)
- J Barber
- Wolfson Laboratories, Biochemistry Department, Imperial College of Science, Technology and Medicine, London, UK
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41
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42
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Durrant JR, Hastings G, Hong Q, Barber J, Porter G, Klug DR. Determination of P680 singlet state lifetimes in photosystem two reaction centres. Chem Phys Lett 1992. [DOI: 10.1016/0009-2614(92)85088-r] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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43
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Blankenship RE. Origin and early evolution of photosynthesis. PHOTOSYNTHESIS RESEARCH 1992; 33:91-111. [PMID: 11538390 DOI: 10.1007/bf00039173] [Citation(s) in RCA: 216] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/1991] [Accepted: 03/12/1992] [Indexed: 05/24/2023]
Abstract
Photosynthesis was well-established on the earth at least 3.5 thousand million years ago, and it is widely believed that these ancient organisms had similar metabolic capabilities to modern cyanobacteria. This requires that development of two photosystems and the oxygen evolution capability occurred very early in the earth's history, and that a presumed phase of evolution involving non-oxygen evolving photosynthetic organisms took place even earlier. The evolutionary relationships of the reaction center complexes found in all the classes of currently existing organisms have been analyzed using sequence analysis and biophysical measurements. The results indicate that all reaction centers fall into two basic groups, those with pheophytin and a pair of quinones as early acceptors, and those with iron sulfur clusters as early acceptors. No simple linear branching evolutionary scheme can account for the distribution patterns of reaction centers in existing photosynthetic organisms, and lateral transfer of genetic information is considered as a likely possibility. Possible scenarios for the development of primitive reaction centers into the heterodimeric protein structures found in existing reaction centers and for the development of organisms with two linked photosystems are presented.
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Affiliation(s)
- R E Blankenship
- Department of Chemistry and Biochemistry, Arizona State University, Tempe 85287-1604, USA
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44
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Bockholt R, Masepohl B, Pistorius EK. Insertional inactivation of the psbO gene encoding the manganese stabilizing protein of photosystem II in the cyanobacterium Synechococcus PCC7942. Effect on photosynthetic water oxidation and L-amino acid oxidase activity. FEBS Lett 1991; 294:59-63. [PMID: 1660410 DOI: 10.1016/0014-5793(91)81343-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A Synechococcus PCC7942 mutant in which the psbO gene was inactivated by insertion of a chloramphenicol interposon and which did not contain any detectable manganese stabilizing protein in immunoblot experiments, was constructed. Such a Synechococcus mutant was able to grow under photoautotrophic conditions. Isolated thylakoid membranes from the mutant required addition of CaCl2 and MnCl2 for photosynthetic O2 evolution, and the detectable L-amino acid oxidase activity in the isolated thylakoid membranes from the mutant was approximately four times higher than in wild-type thylakoids. The results are discussed with respect to our model suggesting that the water-oxidizing enzyme may have evolved from a flavoprotein with L-amino acid dehydrogenase/oxidase activity.
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Affiliation(s)
- R Bockholt
- Lehstuhl für Zellphysiologie, Universität Bielefeld, Germany
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45
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Draber W, Kluth JF, Tietjen K, Trebst A. Herbizide in der Photosyntheseforschung. Angew Chem Int Ed Engl 1991. [DOI: 10.1002/ange.19911031210] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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46
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Barbato R, Shipton CA, Giacometti GM, Barber J. New evidence suggests that the initial photoinduced cleavage of the D1-protein may not occur near the PEST sequence. FEBS Lett 1991; 290:162-6. [PMID: 1915869 DOI: 10.1016/0014-5793(91)81250-c] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
When isolated reaction centres of photosystem 2 from pea or wheat are exposed to photoinhibitory illumination in the presence of an electron acceptor, breakdown products of the D1-protein are observed having molecular masses ranging from about 24 to 10 kDa. By using antibodies raised to the C-terminal or N-terminal portions of D1 it was shown that the major breakdown fragment of 24 kDa was derived from the C-terminus. This conclusion was supported by phosphorylation studies and from the digestion pattern obtained by lysine specific endoprotease-induced proteolysis. The complementary N-terminal breakdown fragment was found to have an apparent molecular mass of 10 kDa. The implications of these data are discussed in terms of the possible relationship between the 24 kDa C-terminal fragment and the 23.5 kDa breakdown fragment detected in vivo by Greenberg et al. [1987, EMBO J. 6, 2865-2869] and it is suggested, based on limited proteolysis using papain, that the latter may not be derived from the N-terminus as previously thought but also originates from the C-terminus.
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Affiliation(s)
- R Barbato
- AFRC Photosynthesis Research Group, Wolfson Laboratories, Biochemistry Department, Imperial College of Science, Technology and Medicine, London, UK
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47
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The isolated D1/D2/cyt b-559 reaction centre complex of Photosystem II possesses a serine-type endopeptidase activity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1991. [DOI: 10.1016/s0005-2728(05)80209-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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48
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Booth PJ, Crystall B, Ahmad I, Barber J, Porter G, Klug DR. Observation of multiple radical pair states in photosystem 2 reaction centers. Biochemistry 1991; 30:7573-86. [PMID: 1854756 DOI: 10.1021/bi00244a029] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Charge recombination of the primary radical pair in D1/D2 reaction centers from photosystem 2 has been studied by time-resolved fluorescence and absorption spectroscopy. The kinetics of the primary radical pair are multiexponential and exhibit at least two lifetimes of 20 and 52 ns. In addition, a third lifetime of approximately 500 ps also appears to be present. These multiexponential charge-recombination kinetics reflect either different conformational states of D1/D2 reaction centers, with the different conformers exhibiting different radical pair lifetimes, or relaxations in the free energy of the radical pair state. Whichever model is invoked, the free energies of formation of the different radical pair states exhibit a linear temperature dependence from 100 to 220 K, indicating that they are dominated by entropy with negligible enthalpy contributions. These results are in agreement with previous determinations of the thermodynamics that govern primary charge separation in both D1/D2 reaction centers [Booth, P.J., Crystall, B., Giorgi, L. B., Barber, J., Klug, D.R., & Porter, G. (1990) Biochim. Biophys. Acta 1016, 141-152] and reaction centers of purple bacteria [Woodbury, N.W.T., & Parson, W.W. (1984) Biochim. Biophys. Acta 767, 345-361]. It is possible that these observations reflect structural changes that accompanying primary charge separation and assist in stabilization of the radical pair state thus optimizing the efficiency of primary electron transfer.
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Affiliation(s)
- P J Booth
- Photochemistry Research Group, Department of Biology, Imperial College, London, U.K
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49
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Newell W, Amerongen HV, Barber J, van Grondelle R. Spectroscopic characterisation of the reaction centre of photosystem II using polarised light: Evidence for β-carotene excitons in PS II reaction centres. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1991. [DOI: 10.1016/s0005-2728(05)80106-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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50
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Gounaris K, Chapman DJ, Booth P, Crystall B, Giorgi LB, Klug DR, Porter G, Barber J. Comparison of the D1/D2/cytochrome b559 reaction centre complex of photosystem two isolated by two different methods. FEBS Lett 1990; 265:88-92. [PMID: 2194834 DOI: 10.1016/0014-5793(90)80890-u] [Citation(s) in RCA: 117] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Photosystem 2 reaction centre complexes prepared either by solubilisation with Triton X-100 and subsequent exchange into dodecyl maltoside or by a procedure involving a combination of dodecyl maltoside and LiClO4, were characterised in terms of chlorophyll a, pheophytin a, beta-carotene and cytochrome b559 content. Time-resolved chlorophyll fluorescence decay kinetics were measured using both types of complexes. Our data show that the isolated photosystem two reaction centre complex contain, for two pheophytin a molecules, close to six chlorophyll a, two beta-carotene and one cytochrome b559. No major differences were observed in the composition or the kinetic characteristics measured in the samples prepared by the different procedures. Time-resolved fluorescence measurements indicate that more than 94% of the chlorophyll a in both preparations is coupled to the reaction centre complex.
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Affiliation(s)
- K Gounaris
- Biochemistry Department, Imperial College, London, UK
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