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Krysiak S, Burda K. The Effect of Removal of External Proteins PsbO, PsbP and PsbQ on Flash-Induced Molecular Oxygen Evolution and Its Biphasicity in Tobacco PSII. Curr Issues Mol Biol 2024; 46:7187-7218. [PMID: 39057069 PMCID: PMC11276211 DOI: 10.3390/cimb46070428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2024] [Revised: 06/30/2024] [Accepted: 07/02/2024] [Indexed: 07/28/2024] Open
Abstract
The oxygen evolution within photosystem II (PSII) is one of the most enigmatic processes occurring in nature. It is suggested that external proteins surrounding the oxygen-evolving complex (OEC) not only stabilize it and provide an appropriate ionic environment but also create water channels, which could be involved in triggering the ingress of water and the removal of O2 and protons outside the system. To investigate the influence of these proteins on the rate of oxygen release and the efficiency of OEC function, we developed a measurement protocol for the direct measurement of the kinetics of oxygen release from PSII using a Joliot-type electrode. PSII-enriched tobacco thylakoids were used in the experiments. The results revealed the existence of slow and fast modes of oxygen evolution. This observation is model-independent and requires no specific assumptions about the initial distribution of the OEC states. The gradual removal of exogenous proteins resulted in a slowdown of the rapid phase (~ms) of O2 release and its gradual disappearance while the slow phase (~tens of ms) accelerated. The role of external proteins in regulating the biphasicity and efficiency of oxygen release is discussed based on observed phenomena and current knowledge.
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Affiliation(s)
| | - Kvetoslava Burda
- Faculty of Physics and Applied Computer Science, AGH University of Krakow, al. Mickiewicza 30, 30-059 Krakow, Poland;
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2
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Gates C, Williams JM, Ananyev G, Dismukes GC. How chloride functions to enable proton conduction in photosynthetic water oxidation: Time-resolved kinetics of intermediates (S-states) in vivo and bromide substitution. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148998. [PMID: 37499962 DOI: 10.1016/j.bbabio.2023.148998] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 07/11/2023] [Accepted: 07/19/2023] [Indexed: 07/29/2023]
Abstract
Chloride (Cl-) is essential for O2 evolution during photosynthetic water oxidation. Two chlorides near the water-oxidizing complex (WOC) in Photosystem II (PSII) structures from Thermosynechococcus elongatus (and T. vulcanus) have been postulated to transfer protons generated from water oxidation. We monitored four criteria: primary charge separation flash yield (P* → P+QA-), rates of water oxidation steps (S-states), rate of proton evolution, and flash O2 yield oscillations by measuring chlorophyll variable fluorescence (P* quenching), pH-sensitive dye changes, and oximetry. Br-substitution slows and destabilizes cellular growth, resulting from lower light-saturated O2 evolution rate (-20 %) and proton release (-36 % ΔpH gradient). The latter implies less ATP production. In Br- cultures, protonogenic S-state transitions (S2 → S3 → S0') slow with increasing light intensity and during O2/water exchange (S0' → S0 → S1), while the non-protonogenic S1 → S2 transition is kinetically unaffected. As flash rate increases in Cl- cultures, both rate and extent of acidification of the lumen increase, while charge recombination is suppressed relative to Br-. The Cl- advantage in rapid proton escape from the WOC to lumen is attributed to correlated ion-pair movement of H3O+Cl- in dry water channels vs. separated Br- and H+ ion movement through different regions (>200-fold difference in Bronsted acidities). By contrast, at low flash rates a previously unreported reversal occurs that favors Br- cultures for both proton evolution and less PSII charge recombination. In Br- cultures, slower proton transfer rate is attributed to stronger ion-pairing of Br- with AA residues lining the water channels. Both anions charge-neutralize protons and shepherd them to the lumen using dry aqueous channels.
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Affiliation(s)
- Colin Gates
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Computational Biology and Molecular Biophysics, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemistry and Biochemistry, Loyola University Chicago, IL 60660, USA
| | - Jonah M Williams
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, NJ 08854, USA
| | - Gennady Ananyev
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, NJ 08854, USA
| | - G Charles Dismukes
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, NJ 08854, USA; Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, NJ 08854, USA.
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Imaizumi K, Ifuku K. Binding and functions of the two chloride ions in the oxygen-evolving center of photosystem II. PHOTOSYNTHESIS RESEARCH 2022; 153:135-156. [PMID: 35698013 DOI: 10.1007/s11120-022-00921-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 05/02/2022] [Indexed: 06/15/2023]
Abstract
Light-driven water oxidation in photosynthesis occurs at the oxygen-evolving center (OEC) of photosystem II (PSII). Chloride ions (Cl-) are essential for oxygen evolution by PSII, and two Cl- ions have been found to specifically bind near the Mn4CaO5 cluster in the OEC. The retention of these Cl- ions within the OEC is critically supported by some of the membrane-extrinsic subunits of PSII. The functions of these two Cl- ions and the mechanisms of their retention both remain to be fully elucidated. However, intensive studies performed recently have advanced our understanding of the functions of these Cl- ions, and PSII structures from various species have been reported, aiding the interpretation of previous findings regarding Cl- retention by extrinsic subunits. In this review, we summarize the findings to date on the roles of the two Cl- ions bound within the OEC. Additionally, together with a short summary of the functions of PSII membrane-extrinsic subunits, we discuss the mechanisms of Cl- retention by these extrinsic subunits.
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Affiliation(s)
- Ko Imaizumi
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan
| | - Kentaro Ifuku
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan.
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Haddy A, Lee I, Shin K, Tai H. Characterization of fluoride inhibition in photosystem II lacking extrinsic PsbP and PsbQ subunits. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2018; 185:1-9. [DOI: 10.1016/j.jphotobiol.2018.05.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 05/15/2018] [Accepted: 05/18/2018] [Indexed: 10/16/2022]
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5
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Baranov S, Haddy A. An enzyme kinetics study of the pH dependence of chloride activation of oxygen evolution in photosystem II. PHOTOSYNTHESIS RESEARCH 2017; 131:317-332. [PMID: 27896527 DOI: 10.1007/s11120-016-0325-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 11/16/2016] [Indexed: 06/06/2023]
Abstract
Oxygen evolution by photosystem II (PSII) involves activation by Cl- ion, which is regulated by extrinsic subunits PsbQ and PsbP. In this study, the kinetics of chloride activation of oxygen evolution was studied in preparations of PSII depleted of the PsbQ and PsbP subunits (NaCl-washed and Na2SO4/pH 7.5-treated) over a pH range from 5.3 to 8.0. At low pH, activation by chloride was followed by inhibition at chloride concentrations >100 mM, whereas at high pH activation continued as the chloride concentration increased above 100 mM. Both activation and inhibition were more pronounced at lower pH, indicating that Cl- binding depended on protonation events in each case. The simplest kinetic model that could account for the complete data set included binding of Cl- at two sites, one for activation and one for inhibition, and four protonation steps. The intrinsic (pH-independent) dissociation constant for Cl- activation, K S, was found to be 0.9 ± 0.2 mM for both preparations, and three of the four pK as were determined, with the fourth falling below the pH range studied. The intrinsic inhibition constant, K I, was found to be 64 ± 2 and 103 ± 7 mM for the NaCl-washed and Na2SO4/pH7.5-treated preparations, respectively, and is considered in terms of the conditions likely to be present in the thylakoid lumen. This enzyme kinetics analysis provides a more complete characterization of chloride and pH dependence of O2 evolution activity than has been previously presented.
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Affiliation(s)
- Sergei Baranov
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, 27402, USA
| | - Alice Haddy
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, 27402, USA.
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Najafpour MM, Heidari S, Balaghi SE, Hołyńska M, Sadr MH, Soltani B, Khatamian M, Larkum AW, Allakhverdiev SI. Proposed mechanisms for water oxidation by Photosystem II and nanosized manganese oxides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:156-174. [DOI: 10.1016/j.bbabio.2016.11.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 11/05/2016] [Accepted: 11/08/2016] [Indexed: 12/18/2022]
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7
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Najafpour MM, Fekete M, Sedigh DJ, Aro EM, Carpentier R, Eaton-Rye JJ, Nishihara H, Shen JR, Allakhverdiev SI, Spiccia L. Damage Management in Water-Oxidizing Catalysts: From Photosystem II to Nanosized Metal Oxides. ACS Catal 2015. [DOI: 10.1021/cs5015157] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
| | - Monika Fekete
- School of Chemistry and the ARC Centre of Excellence for Electromaterials Science, Monash University, Victoria 3800, Australia
| | | | - Eva-Mari Aro
- Department of Biochemistry and Food Chemistry, University of Turku, FI-20014 Turku, Finland
| | - Robert Carpentier
- Groupe de Recherche en Biologie Végétale (GRBV), Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, Québec G9A 5H7, Canada
| | - Julian J. Eaton-Rye
- Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Hiroshi Nishihara
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Jian-Ren Shen
- Photosynthesis Research Center, Graduate School of Natural Science and Technology/Faculty of Science, Okayama University, Okayama 700-8530, Japan
| | - Suleyman I. Allakhverdiev
- Controlled Photobiosynthesis Laboratory, Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, Moscow 127276, Russia
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia
- Department of Plant Physiology, Faculty of Biology, M. V. Lomonosov Moscow State University, Leninskie Gory 1-12, Moscow 119991, Russia
| | - Leone Spiccia
- School of Chemistry and the ARC Centre of Excellence for Electromaterials Science, Monash University, Victoria 3800, Australia
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8
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Zhang Z, Coats KL, Chen Z, Hubin TJ, Yin G. Influence of Calcium(II) and Chloride on the Oxidative Reactivity of a Manganese(II) Complex of a Cross-Bridged Cyclen Ligand. Inorg Chem 2014; 53:11937-47. [DOI: 10.1021/ic501342c] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Zhan Zhang
- Key
Laboratory for Large-Format Battery Materials and System, Ministry
of Education, School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Katherine L. Coats
- Department
of Chemistry and Physics, Southwestern Oklahoma State University, 100
Campus Drive, Weatherford, Oklahoma 73096, United States
| | - Zhuqi Chen
- Key
Laboratory for Large-Format Battery Materials and System, Ministry
of Education, School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Timothy J. Hubin
- Department
of Chemistry and Physics, Southwestern Oklahoma State University, 100
Campus Drive, Weatherford, Oklahoma 73096, United States
| | - Guochuan Yin
- Key
Laboratory for Large-Format Battery Materials and System, Ministry
of Education, School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
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Cationic screening of charged surface groups (carboxylates) affects electron transfer steps in photosystem-II water oxidation and quinone reduction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1625-34. [DOI: 10.1016/j.bbabio.2014.07.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 07/14/2014] [Accepted: 07/16/2014] [Indexed: 11/23/2022]
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10
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Wang L, Zhang C, Zhao J. Location and function of the high-affinity chloride in the oxygen-evolving complex – Implications from comparing studies on Cl−/Br−/I−-substituted photosystem II prepared using two different methods. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2014; 138:249-55. [DOI: 10.1016/j.jphotobiol.2014.05.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 05/22/2014] [Accepted: 05/26/2014] [Indexed: 11/17/2022]
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11
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Pokhrel R, Service RJ, Debus RJ, Brudvig GW. Mutation of Lysine 317 in the D2 Subunit of Photosystem II Alters Chloride Binding and Proton Transport. Biochemistry 2013; 52:4758-73. [DOI: 10.1021/bi301700u] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Ravi Pokhrel
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107,
United States
| | - Rachel J. Service
- Department
of Biochemistry, University of California, Riverside, California 92521,
United States
| | - Richard J. Debus
- Department
of Biochemistry, University of California, Riverside, California 92521,
United States
| | - Gary W. Brudvig
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107,
United States
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12
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Computational Studies of the Oxygen-Evolving Complex of Photosystem II and Biomimetic Oxomanganese Complexes for Renewable Energy Applications. ACTA ACUST UNITED AC 2013. [DOI: 10.1021/bk-2013-1133.ch011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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13
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Pokhrel R, Brudvig GW. Investigation of the inhibitory effect of nitrite on Photosystem II. Biochemistry 2013; 52:3781-9. [PMID: 23631466 DOI: 10.1021/bi400206q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The role of chloride in photosystem II (PSII) is unclear. Several monovalent anions compete for the Cl(-) site(s) in PSII, and some even support activity. NO2(-) has been reported to be an activator in Cl(-)-depleted PSII membranes. In this paper, we report a detailed investigation of the chemistry of NO2(-) with PSII. NO2(-) is shown to inhibit PSII activity, and the effects on the donor side as well as the acceptor side are characterized using steady-state O2-evolution assays, electron paramagnetic resonance (EPR) spectroscopy, electron-transfer assays, and flash-induced polarographic O2 yield measurements. Enzyme kinetics analysis shows multiple sites of NO2(-) inhibition in PSII with significant inhibition of oxygen evolution at <5 mM NO2(-). By EPR spectroscopy, the yield of the S2 state remains unchanged up to 15 mM NO2(-). However, the S2-state g = 4.1 signal is favored over the g = 2 multiline signal with increasing NO2(-) concentrations. This could indicate competition of NO2(-) for the Cl(-) site at higher NO2(-) concentrations. In addition to the donor-side chemistry, there is clear evidence of an acceptor-side effect of NO2(-). The g = 1.9 Fe(II)-QA(-•) signal is replaced by a broad g = 1.6 signal in the presence of NO2(-). Additionally, a g = 1.8 Fe(II)-Q(-•) signal is present in the dark, indicating the formation of a NO2(-)-bound Fe(II)-QB(-•) species in the dark. Electron-transfer assays suggest that the inhibitory effect of NO2(-) on the activity of PSII is largely due to the donor-side chemistry of NO2(-). UV-visible spectroscopy and flash-induced polarographic O2 yield measurements indicate that NO2(-) is oxidized by the oxygen-evolving complex in the higher S states, contributing to the donor-side inhibition by NO2(-).
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Affiliation(s)
- Ravi Pokhrel
- Department of Chemistry, Yale University , New Haven, Connecticut 06520-8107, United States
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14
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Boussac A, Ishida N, Sugiura M, Rappaport F. Probing the role of chloride in Photosystem II from Thermosynechococcus elongatus by exchanging chloride for iodide. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:802-10. [DOI: 10.1016/j.bbabio.2012.02.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 02/21/2012] [Accepted: 02/24/2012] [Indexed: 11/29/2022]
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15
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Dau H, Zaharieva I, Haumann M. Recent developments in research on water oxidation by photosystem II. Curr Opin Chem Biol 2012; 16:3-10. [DOI: 10.1016/j.cbpa.2012.02.011] [Citation(s) in RCA: 177] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 02/08/2012] [Accepted: 02/10/2012] [Indexed: 11/27/2022]
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16
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Grundmeier A, Dau H. Structural models of the manganese complex of photosystem II and mechanistic implications. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:88-105. [PMID: 21787743 DOI: 10.1016/j.bbabio.2011.07.004] [Citation(s) in RCA: 191] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 07/06/2011] [Accepted: 07/08/2011] [Indexed: 11/29/2022]
Abstract
Photosynthetic water oxidation and O₂ formation are catalyzed by a Mn₄Ca complex bound to the proteins of photosystem II (PSII). The catalytic site, including the inorganic Mn₄CaO(n)H(x) core and its protein environment, is denoted as oxygen-evolving complex (OEC). Earlier and recent progress in the endeavor to elucidate the structure of the OEC is reviewed, with focus on recent results obtained by (i) X−ray spectroscopy (specifically by EXAFS analyses), and (ii) X-ray diffraction (XRD, protein crystallography). Very recently, an impressive resolution of 1.9Å has been achieved by XRD. Most likely however, all XRD data on the Mn₄CaO(n)H(x) core of the OEC are affected by X-ray induced modifications (radiation damage). Therefore and to address (important) details of the geometric and electronic structure of the OEC, a combined analysis of XRD and XAS data has been approached by several research groups. These efforts are reviewed and extended using an especially comprehensive approach. Taking into account XRD results on the protein environment of the inorganic core of the Mn complex, 12 alternative OEC models are considered and evaluated by quantitative comparison to (i) extended-range EXAFS data, (ii) polarized EXAFS of partially oriented PSII membrane particles, and (iii) polarized EXAFS of PSII crystals. We conclude that there is a class of OEC models that is in good agreement with both the recent crystallographic models and the XAS data. On these grounds, mechanistic implications for the O−O bond formation chemistry are discussed. This article is part of a Special Issue entitled: Photosystem II.
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Assembly of the water-oxidizing complex in photosystem II. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:204-11. [DOI: 10.1016/j.jphotobiol.2011.02.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 01/27/2011] [Accepted: 02/03/2011] [Indexed: 11/21/2022]
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Rivalta I, Amin M, Luber S, Vassiliev S, Pokhrel R, Umena Y, Kawakami K, Shen JR, Kamiya N, Bruce D, Brudvig GW, Gunner MR, Batista VS. Structural-functional role of chloride in photosystem II. Biochemistry 2011; 50:6312-5. [PMID: 21678923 DOI: 10.1021/bi200685w] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Chloride binding in photosystem II (PSII) is essential for photosynthetic water oxidation. However, the functional roles of chloride and possible binding sites, during oxygen evolution, remain controversial. This paper examines the functions of chloride based on its binding site revealed in the X-ray crystal structure of PSII at 1.9 Å resolution. We find that chloride depletion induces formation of a salt bridge between D2-K317 and D1-D61 that could suppress the transfer of protons to the lumen.
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Affiliation(s)
- Ivan Rivalta
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, USA.
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Pokhrel R, McConnell IL, Brudvig GW. Chloride regulation of enzyme turnover: application to the role of chloride in photosystem II. Biochemistry 2011; 50:2725-34. [PMID: 21366335 DOI: 10.1021/bi2000388] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Chloride-dependent α-amylases, angiotensin-converting enzyme (ACE), and photosystem II (PSII) are activated by bound chloride. Chloride-binding sites in these enzymes contain a positively charged Arg or Lys residue crucial for chloride binding. In α-amylases and ACE, removal of chloride from the binding site triggers formation of a salt bridge between the positively charged Arg or Lys residue involved in chloride binding and a nearby carboxylate residue. The mechanism for chloride activation in ACE and chloride-dependent α-amylases is 2-fold: (i) correctly positioning catalytic residues or other residues involved in stabilizing the enzyme-substrate complex and (ii) fine-tuning of the pKa of a catalytic residue. By using examples of how chloride activates α-amylases and ACE, we can gain insight into the potential mechanisms by which chloride functions in PSII. Recent structural evidence from cyanobacterial PSII indicates that there is at least one chloride-binding site in the vicinity of the oxygen-evolving complex (OEC). Here we propose that, in the absence of chloride, a salt bridge between D2:K317 and D1:D61 (and/or D1:E333) is formed. This can cause a conformational shift of D1:D61 and lower the pKa of this residue, making it an inefficient proton acceptor during the S-state cycle. Movement of the D1:E333 ligand and the adjacent D1:H332 ligand due to chloride removal could also explain the observed change in the magnetic properties of the manganese cluster in the OEC upon chloride depletion.
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Affiliation(s)
- Ravi Pokhrel
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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Cox N, Rapatskiy L, Su JH, Pantazis DA, Sugiura M, Kulik L, Dorlet P, Rutherford AW, Neese F, Boussac A, Lubitz W, Messinger J. Effect of Ca2+/Sr2+ substitution on the electronic structure of the oxygen-evolving complex of photosystem II: a combined multifrequency EPR, 55Mn-ENDOR, and DFT study of the S2 state. J Am Chem Soc 2011; 133:3635-48. [PMID: 21341708 DOI: 10.1021/ja110145v] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electronic structures of the native Mn(4)O(x)Ca cluster and the biosynthetically substituted Mn(4)O(x)Sr cluster of the oxygen evolving complex (OEC) of photosystem II (PSII) core complexes isolated from Thermosynechococcus elongatus, poised in the S(2) state, were studied by X- and Q-band CW-EPR and by pulsed Q-band (55)Mn-ENDOR spectroscopy. Both wild type and tyrosine D less mutants grown photoautotrophically in either CaCl(2) or SrCl(2) containing media were measured. The obtained CW-EPR spectra of the S(2) state displayed the characteristic, clearly noticeable differences in the hyperfine pattern of the multiline EPR signal [Boussac et al. J. Biol. Chem.2004, 279, 22809-22819]. In sharp contrast, the manganese ((55)Mn) ENDOR spectra of the Ca and Sr forms of the OEC were remarkably similar. Multifrequency simulations of the X- and Q-band CW-EPR and (55)Mn-pulsed ENDOR spectra using the Spin Hamiltonian formalism were performed to investigate this surprising result. It is shown that (i) all four manganese ions contribute to the (55)Mn-ENDOR spectra; (ii) only small changes are seen in the fitted isotropic hyperfine values for the Ca(2+) and Sr(2+) containing OEC, suggesting that there is no change in the overall spin distribution (electronic coupling scheme) upon Ca(2+)/Sr(2+) substitution; (iii) the changes in the CW-EPR hyperfine pattern can be explained by a small decrease in the anisotropy of at least two hyperfine tensors. It is proposed that modifications at the Ca(2+) site may modulate the fine structure tensor of the Mn(III) ion. DFT calculations support the above conclusions. Our data analysis also provides strong support for the notion that in the S(2) state the coordination of the Mn(III) ion is square-pyramidal (5-coordinate) or octahedral (6-coordinate) with tetragonal elongation. In addition, it is shown that only one of the currently published OEC models, the Siegbahn structure [Siegbahn, P. E. M. Acc. Chem. Res.2009, 42, 1871-1880, Pantazis, D. A. et al. Phys. Chem. Chem. Phys.2009, 11, 6788-6798], is consistent with all data presented here. These results provide important information for the structure of the OEC and the water-splitting mechanism. In particular, the 5-coordinate Mn(III) is a potential site for substrate 'water' (H(2)O, OH(-)) binding. Its location within the cuboidal structural unit, as opposed to the external 'dangler' position, may have important consequences for the mechanism of O-O bond formation.
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Affiliation(s)
- Nicholas Cox
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
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Dau H, Limberg C, Reier T, Risch M, Roggan S, Strasser P. The Mechanism of Water Oxidation: From Electrolysis via Homogeneous to Biological Catalysis. ChemCatChem 2010. [DOI: 10.1002/cctc.201000126] [Citation(s) in RCA: 1320] [Impact Index Per Article: 94.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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22
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Liebisch P, Dau H. Linear Dichroism in the XANES of Partially Oriented Samples: Theory and Application to the Photosynthetic Manganese Complex. Chemphyschem 2010; 11:1236-47. [DOI: 10.1002/cphc.200900954] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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23
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Guskov A, Gabdulkhakov A, Broser M, Glöckner C, Hellmich J, Kern J, Frank J, Müh F, Saenger W, Zouni A. Recent Progress in the Crystallographic Studies of Photosystem II. Chemphyschem 2010; 11:1160-71. [DOI: 10.1002/cphc.200900901] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Ren Y, Zhang C, Zhao J. Substitution of chloride by bromide modifies the low-temperature tyrosine Z oxidation in active photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1421-7. [PMID: 20206122 DOI: 10.1016/j.bbabio.2010.02.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2009] [Revised: 01/29/2010] [Accepted: 02/23/2010] [Indexed: 11/19/2022]
Abstract
Chloride is an essential cofactor for photosynthetic water oxidation. However, its location and functional roles in active photosystem II are still a matter of debate. We have investigated this issue by studying the effects of Cl- replacement by Br- in active PSII. In Br- substituted samples, Cl- is effectively replaced by Br- in the presence of 1.2 M NaBr under room light with protection of anaerobic atmosphere followed by dialysis. The following results have been obtained. i) The oxygen-evolving activities of the Br--PSII samples are significantly lower than that of the Cl--PSII samples; ii) The same S2 multiline EPR signals are observed in both Br- and Cl--PSII samples; iii) The amplitudes of the visible light induced S1TyrZ* and S2TyrZ* EPR signals are significantly decreased after Br- substitution; the S1TyrZ* EPR signal is up-shifted about 8G, whereas the S2TyrZ* signal is down-shifted about 12 G after Br- substitution. These results imply that the redox properties of TyrZ and spin interactions between TyrZ* and Mn-cluster could be significantly modified due to Br- substitution. It is suggested that Cl-/Br- probably coordinates to the Ca2+ ion of the Mn-cluster in active photosystem II.
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Affiliation(s)
- Yanan Ren
- Laboratory of Photochemistry, Beijing National Laboratory of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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Yano J, Yachandra VK. X-ray absorption spectroscopy. PHOTOSYNTHESIS RESEARCH 2009; 102:241-54. [PMID: 19653117 PMCID: PMC2777224 DOI: 10.1007/s11120-009-9473-8] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 07/09/2009] [Indexed: 05/20/2023]
Abstract
This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn(4)Ca cluster in Photosystem II is presented.
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Affiliation(s)
- Junko Yano
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 USA
| | - Vittal K. Yachandra
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 USA
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Kuntzleman TS, Haddy A. Fluoride inhibition of photosystem II and the effect of removal of the PsbQ subunit. PHOTOSYNTHESIS RESEARCH 2009; 102:7-19. [PMID: 19633919 DOI: 10.1007/s11120-009-9469-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2009] [Accepted: 07/06/2009] [Indexed: 05/28/2023]
Abstract
Photosystem II (PSII), the light-absorbing complex of photosynthesis that evolves oxygen, requires chloride for activation of the oxygen evolving complex (OEC). In this study, fluoride was characterized as an inhibitor of Cl(-)-activated oxygen evolution in higher plant PSII. It was confirmed to be primarily a competitive inhibitor in intact PSII, with Cl(-)-competitive inhibition constant K(i) = 2 mM and uncompetitive inhibition constant K'(1) = 79 mM. A pH dependence study showed that fluoride inhibition was more pronounced at lower pH values. In order to determine the location of the fluoride effect, PSII preparations lacking various amounts of the PsbQ subunit were prepared. The competitive F(-) inhibition constant and the Michaelis constant for Cl(-) activation increased with loss of the PsbQ subunit, while the uncompetitive F(-) inhibition constant was relatively insensitive to loss of PsbQ. The S(2) state EPR signals from PSII lacking PsbQ responded to Ca(2+) and Cl(-) removal and to F(-) treatment similar to intact PSII, with enhancement of the g = 4.1 signal and suppression of the multiline signal, but the effects were more pronounced in PSII lacking PsbQ. Together, these results support the interpretation that the PsbQ subunit has a role in retaining anions within the OEC.
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Affiliation(s)
- Thomas S Kuntzleman
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC 27402, USA
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Location of chloride and its possible functions in oxygen-evolving photosystem II revealed by X-ray crystallography. Proc Natl Acad Sci U S A 2009; 106:8567-72. [PMID: 19433803 PMCID: PMC2688974 DOI: 10.1073/pnas.0812797106] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The chloride ion, Cl(-), is an essential cofactor for oxygen evolution of photosystem II (PSII) and is closely associated with the Mn(4)Ca cluster. Its detailed location and function have not been identified, however. We substituted Cl(-) with a bromide ion (Br(-)) or an iodide ion (I(-)) in PSII and analyzed the crystal structures of PSII with Br(-) and I(-) substitutions. Substitution of Cl(-) with Br(-) did not inhibit oxygen evolution, whereas substitution of Cl(-) with I(-) completely inhibited oxygen evolution, indicating the efficient replacement of Cl(-) by I(-). PSII with Br(-) and I(-) substitutions were crystallized, and their structures were analyzed. The results showed that there are 2 anion-binding sites in each PSII monomer; they are located on 2 sides of the Mn(4)Ca cluster at equal distances from the metal cluster. Anion-binding site 1 is close to the main chain of D1-Glu-333, and site 2 is close to the main chain of CP43-Glu-354; these 2 residues are coordinated directly with the Mn(4)Ca cluster. In addition, site 1 is located in the entrance of a proton exit channel. These results indicate that these 2 Cl(-) anions are required to maintain the coordination structure of the Mn(4)Ca cluster as well as the proposed proton channel, thereby keeping the oxygen-evolving complex fully active.
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Cyanobacterial photosystem II at 2.9-A resolution and the role of quinones, lipids, channels and chloride. Nat Struct Mol Biol 2009; 16:334-42. [PMID: 19219048 DOI: 10.1038/nsmb.1559] [Citation(s) in RCA: 867] [Impact Index Per Article: 57.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 01/14/2009] [Indexed: 12/11/2022]
Abstract
Photosystem II (PSII) is a large homodimeric protein-cofactor complex located in the photosynthetic thylakoid membrane that acts as light-driven water:plastoquinone oxidoreductase. The crystal structure of PSII from Thermosynechococcus elongatus at 2.9-A resolution allowed the unambiguous assignment of all 20 protein subunits and complete modeling of all 35 chlorophyll a molecules and 12 carotenoid molecules, 25 integral lipids and 1 chloride ion per monomer. The presence of a third plastoquinone Q(C) and a second plastoquinone-transfer channel, which were not observed before, suggests mechanisms for plastoquinol-plastoquinone exchange, and we calculated other possible water or dioxygen and proton channels. Putative oxygen positions obtained from a Xenon derivative indicate a role for lipids in oxygen diffusion to the cytoplasmic side of PSII. The chloride position suggests a role in proton-transfer reactions because it is bound through a putative water molecule to the Mn(4)Ca cluster at a distance of 6.5 A and is close to two possible proton channels.
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Pantazis DA, Orio M, Petrenko T, Zein S, Lubitz W, Messinger J, Neese F. Structure of the oxygen-evolving complex of photosystem II: information on the S2 state through quantum chemical calculation of its magnetic properties. Phys Chem Chem Phys 2009; 11:6788-98. [DOI: 10.1039/b907038a] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Renger G, Renger T. Photosystem II: The machinery of photosynthetic water splitting. PHOTOSYNTHESIS RESEARCH 2008; 98:53-80. [PMID: 18830685 DOI: 10.1007/s11120-008-9345-7] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Accepted: 07/29/2008] [Indexed: 05/26/2023]
Abstract
This review summarizes our current state of knowledge on the structural organization and functional pattern of photosynthetic water splitting in the multimeric Photosystem II (PS II) complex, which acts as a light-driven water: plastoquinone-oxidoreductase. The overall process comprises three types of reaction sequences: (1) photon absorption and excited singlet state trapping by charge separation leading to the ion radical pair [Formula: see text] formation, (2) oxidative water splitting into four protons and molecular dioxygen at the water oxidizing complex (WOC) with P680+* as driving force and tyrosine Y(Z) as intermediary redox carrier, and (3) reduction of plastoquinone to plastoquinol at the special Q(B) binding site with Q(A)-* acting as reductant. Based on recent progress in structure analysis and using new theoretical approaches the mechanism of reaction sequence (1) is discussed with special emphasis on the excited energy transfer pathways and the sequence of charge transfer steps: [Formula: see text] where (1)(RC-PC)* denotes the excited singlet state (1)P680* of the reaction centre pigment complex. The structure of the catalytic Mn(4)O(X)Ca cluster of the WOC and the four step reaction sequence leading to oxidative water splitting are described and problems arising for the electronic configuration, in particular for the nature of redox state S(3), are discussed. The unravelling of the mode of O-O bond formation is of key relevance for understanding the mechanism of the process. This problem is not yet solved. A multistate model is proposed for S(3) and the functional role of proton shifts and hydrogen bond network(s) is emphasized. Analogously, the structure of the Q(B) site for PQ reduction to PQH(2) and the energetic and kinetics of the two step redox reaction sequence are described. Furthermore, the relevance of the protein dynamics and the role of water molecules for its flexibility are briefly outlined. We end this review by presenting future perspectives on the water oxidation process.
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Affiliation(s)
- Gernot Renger
- Max Volmer Laboratory for Biophysical Chemistry, Berlin Institute of Technology, Berlin, Germany.
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31
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Abstract
In oxygenic photosynthesis, photosystem II (PSII) is the multisubunit membrane protein responsible for the oxidation of water to O2 and the reduction of plastoquinone to plastoquinol. One electron charge separation in the PSII reaction center is coupled to sequential oxidation reactions at the oxygen-evolving complex (OEC), which is composed of four manganese ions and one calcium ion. The sequentially oxidized forms of the OEC are referred to as the S(n) states. S(1) is the dark-adapted state of the OEC. Flash-induced oxygen production oscillates with period four and occurs during the S(3) to S(0) transition. Chloride plays an important, but poorly understood role in photosynthetic water oxidation. Chloride removal is known to block manganese oxidation during the S(2) to S(3) transition. In this work, we have used azide as a probe of proton transfer reactions in PSII. PSII was sulfate-treated to deplete chloride and then treated with azide. Steady state oxygen evolution measurements demonstrate that azide inhibits oxygen evolution in a chloride-dependent manner and that azide is a mixed or noncompetitive inhibitor. This result is consistent with two azide binding sites, one at which azide competes with chloride and one at which azide and chloride do not compete. At pH 7.5, the K(i) for the competing site was estimated as 1 mM, and the K(i)' for the uncompetitive site was estimated as 8 mM. Vibrational spectroscopy was then used to monitor perturbations in the frequency and amplitude of the azide antisymmetric stretching band. These changes were induced by laser-induced charge separation in the PSII reaction center. The results suggest that azide is involved in proton transfer reactions, which occur before manganese oxidation, on the donor side of chloride-depleted PSII.
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Dau H, Grundmeier A, Loja P, Haumann M. On the structure of the manganese complex of photosystem II: extended-range EXAFS data and specific atomic-resolution models for four S-states. Philos Trans R Soc Lond B Biol Sci 2008; 363:1237-43; discussion 1243-4. [PMID: 17989002 DOI: 10.1098/rstb.2007.2220] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The water-oxidizing manganese complex bound to the proteins of photosystem II (PSII) was studied by X-ray absorption spectroscopy on PSII membrane particles. An extended range for collection of extended X-ray absorption fine-structure (EXAFS) data was used (up to 16.6A(-1)). The EXAFS suggests the presence of two Mn-Mn distances close to 2.7A (per Mn4Ca complex); the existence of a third Mn-Mn distance below 2.9A is at least uncertain. Interestingly, a distance of 3.7A is clearly resolved in the extended-range data and tentatively assigned to a Mn-Mn distance. Taking into account the above EXAFS results (inter alia), we present a model for the structure of the PSII manganese complex, which differs from previous atomic-resolution models. Emphasizing the hypothetical character, we propose for all semi-stable S-states: (i) a structure of the Mn4Ca(mu-O)n core, (ii) a model of the amino acid environment, and (iii) assignments of distinct Mn oxidation states to all the individual Mn ions. This specific working model may permit discussion, verification and invalidation of its various features in comparison with experimental and theoretical findings.
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Affiliation(s)
- Holger Dau
- Freie Universität Berlin, FB Physik, Arnimallee 14, 14195 Berlin, Germany.
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Zein S, Kulik LV, Yano J, Kern J, Pushkar Y, Zouni A, Yachandra VK, Lubitz W, Neese F, Messinger J. Focusing the view on nature's water-splitting catalyst. Philos Trans R Soc Lond B Biol Sci 2008; 363:1167-77; discussion 1177. [PMID: 17989003 DOI: 10.1098/rstb.2007.2212] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Nature invented a catalyst about 3Gyr ago, which splits water with high efficiency into molecular oxygen and hydrogen equivalents (protons and electrons). This reaction is energetically driven by sunlight and the active centre contains relatively cheap and abundant metals: manganese and calcium. This biological system therefore forms the paradigm for all man-made attempts for direct solar fuel production, and several studies are underway to determine the electronic and geometric structures of this catalyst. In this report we briefly summarize the problems and the current status of these efforts and propose a density functional theory-based strategy for obtaining a reliable high-resolution structure of this unique catalyst that includes both the inorganic core and the first ligand sphere.
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Affiliation(s)
- Samir Zein
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
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34
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Ishida N, Sugiura M, Rappaport F, Lai TL, Rutherford AW, Boussac A. Biosynthetic Exchange of Bromide for Chloride and Strontium for Calcium in the Photosystem II Oxygen-evolving Enzymes. J Biol Chem 2008; 283:13330-40. [DOI: 10.1074/jbc.m710583200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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35
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Sproviero EM, Gascón JA, McEvoy JP, Brudvig GW, Batista VS. Quantum Mechanics/Molecular Mechanics Study of the Catalytic Cycle of Water Splitting in Photosystem II. J Am Chem Soc 2008; 130:3428-42. [DOI: 10.1021/ja076130q] [Citation(s) in RCA: 311] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Eduardo M. Sproviero
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107
| | - José A. Gascón
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107
| | - James P. McEvoy
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107
| | - Gary W. Brudvig
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107
| | - Victor S. Batista
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107
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Computational studies of the O(2)-evolving complex of photosystem II and biomimetic oxomanganese complexes. Coord Chem Rev 2008; 252:395-415. [PMID: 19190716 DOI: 10.1016/j.ccr.2007.09.006] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In recent years, there has been considerable interest in studies of catalytic metal clusters in metalloproteins based on Density Functional Theory (DFT) quantum mechanics/molecular mechanics (QM/MM) hybrid methods. These methods explicitly include the perturbational influence of the surrounding protein environment on the structural/functional properties of the catalytic centers. In conjunction with recent breakthroughs in X-ray crystallography and advances in spectroscopic and biophysical studies, computational chemists are trying to understand the structural and mechanistic properties of the oxygen-evolving complex (OEC) embedded in photosystem II (PSII). Recent studies include the development of DFT-QM/MM computational models of the Mn(4)Ca cluster, responsible for photosynthetic water oxidation, and comparative quantum mechanical studies of biomimetic oxomanganese complexes. A number of computational models, varying in oxidation and protonation states and ligation of the catalytic center by amino acid residues, water, hydroxide and chloride have been characterized along the PSII catalytic cycle of water splitting. The resulting QM/MM models are consistent with available mechanistic data, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction data and extended X-ray absorption fine structure (EXAFS) measurements. Here, we review these computational efforts focused towards understanding the catalytic mechanism of water oxidation at the detailed molecular level.
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Sauer K, Yano J, Yachandra VK. X-Ray spectroscopy of the photosynthetic oxygen-evolving complex. Coord Chem Rev 2008; 252:318-335. [PMID: 19190720 PMCID: PMC2387253 DOI: 10.1016/j.ccr.2007.08.009] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Water oxidation to dioxygen in photosynthesis is catalyzed by a Mn(4)Ca cluster with O bridging in Photosystem II (PS II) of plants, algae and cyanobacteria. A variety of spectroscopic methods have been applied to analyzing the participation of the complex. X-ray spectroscopy is particularly useful because it is element-specific, and because it can reveal important structural features of the complex with high accuracy and identify the participation of Mn in the redox chemistry. Following a brief history of the application of X-ray spectroscopy to PS II, an overview of newer results will be presented and a description of the present state of our knowledge based on this approach.
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Affiliation(s)
- Kenneth Sauer
- Department of Chemistry, University of California, Berkeley, CA 94707-5230
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Popelková H, Yocum CF. Current status of the role of Cl(-) ion in the oxygen-evolving complex. PHOTOSYNTHESIS RESEARCH 2007; 93:111-21. [PMID: 17200880 DOI: 10.1007/s11120-006-9121-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 12/04/2006] [Indexed: 05/07/2023]
Abstract
This minireview summarizes the current state of knowledge concerning the role of Cl(-) in the oxygen-evolving complex (OEC) of photosystem II (PSII). The model that proposes that Cl(-) is a Mn ligand is discussed in light of more recent work. Studies of Cl(-) specificity, stoichiometry, kinetics, and retention by extrinsic polypeptides are discussed, as are the results that fail to detect Cl(-) ligation to Mn and results that show a lack of a requirement for Cl(-) in PSII-catalyzed H(2)O oxidation. Mutagenesis experiments in cyanobacteria and higher plants that produce evidence for a correlation between Cl(-) retention and stable interactions among intrinsic and extrinsic polypeptides are summarized, and spectroscopic data on the interaction between PSII and Cl(-) are discussed. Lastly, the question of the site of Cl(-) action in PSII is discussed in connection with the current crystal structures of the enzyme.
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Affiliation(s)
- Hana Popelková
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
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Kern J, Biesiadka J, Loll B, Saenger W, Zouni A. Structure of the Mn4-Ca cluster as derived from X-ray diffraction. PHOTOSYNTHESIS RESEARCH 2007; 92:389-405. [PMID: 17492491 DOI: 10.1007/s11120-007-9173-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Accepted: 04/10/2007] [Indexed: 05/15/2023]
Abstract
The catalytic centre for light-induced water oxidation in photosystem II (PSII) is a multinuclear metal cluster containing four manganese and one calcium cations. Knowing the structure of this biological catalyst is of utmost importance for unravelling the mechanism of water oxidation in photosynthesis. In this review we describe the current state of the X-ray structure determination at 3.0 A resolution of the water oxidation complex (WOC) of PSII. The arrangement of metal cations in the cluster, their coordination and protein surroundings are discussed with regard to spectroscopic and mutagenesis studies. Limitations of the presently available structural data are pointed out and possible perspectives for the future are outlined, including the combination of X-ray diffraction and X-ray spectroscopy on single crystals.
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Affiliation(s)
- Jan Kern
- Institut für Chemie, Max Volmer Laboratorium für Biophysikalische Chemie, Sekr. PC 14, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
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Dau H, Haumann M. Time-resolved X-ray spectroscopy leads to an extension of the classical S-state cycle model of photosynthetic oxygen evolution. PHOTOSYNTHESIS RESEARCH 2007; 92:327-43. [PMID: 17333506 DOI: 10.1007/s11120-007-9141-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Accepted: 01/16/2007] [Indexed: 05/14/2023]
Abstract
In oxygenic photosynthesis, a complete water oxidation cycle requires absorption of four photons by the chlorophylls of photosystem II (PSII). The photons can be provided successively by applying short flashes of light. Already in 1970, Kok and coworkers [Photochem Photobiol 11:457-475, 1970] developed a basic model to explain the flash-number dependence of O2 formation. The third flash applied to dark-adapted PSII induces the S3-->S4-->S0 transition, which is coupled to dioxygen formation at a protein-bound Mn4Ca complex. The sequence of events leading to dioxygen formation and the role of Kok's enigmatic S4-state are only incompletely understood. Recently we have shown by time-resolved X-ray spectroscopy that in the S3-->S0 transition an interesting intermediate is formed, prior to the onset of O-O bond formation [Haumann et al. Science 310:1019-1021, 2005]. The experimental results of the time-resolved X-ray experiments are discussed. The identity of the reaction intermediate is considered and the question is addressed how the novel intermediate is related to the S4-state proposed in 1970 by Bessel Kok. This leads us to an extension of the classical S-state cycle towards a basic model which describes sequence and interplay of electron and proton abstraction events at the donor side of PSII [Dau and Haumann, Science 312:1471-1472, 2006].
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Affiliation(s)
- Holger Dau
- FB Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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41
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Renger G. Oxidative photosynthetic water splitting: energetics, kinetics and mechanism. PHOTOSYNTHESIS RESEARCH 2007; 92:407-25. [PMID: 17647091 DOI: 10.1007/s11120-007-9185-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2006] [Accepted: 04/19/2007] [Indexed: 05/16/2023]
Abstract
This minireview is an attempt to summarize our current knowledge on oxidative water splitting in photosynthesis. Based on the extended Kok model (Kok, Forbush, McGloin (1970) Photochem Photobiol 11:457-476) as a framework, the energetics and kinetics of two different types of reactions comprising the overall process are discussed: (i) P680+* reduction by the redox active tyrosine YZ of polypeptide D1 and (ii) Yz (ox) induced oxidation of the four step sequence in the water oxidizing complex (WOC) leading to the formation of molecular oxygen. The mode of coupling between electron transport (ET) and proton transfer (PT) is of key mechanistic relevance for the redox turnover of YZ and the reactions within the WOC. The peculiar energetics of the oxidation steps in the WOC assure that redox state S1 is thermodynamically most stable. This is a general feature in all oxygen evolving photosynthetic organisms and assumed to be of physiological relevance. The reaction coordinate of oxidative water splitting is discussed on the basis of the available information about the Gibbs energy differences between the individual redox states Si+1 and Si and the data reported for the activation energies of the individual oxidation steps in the WOC. Finally, an attempt is made to cast our current state of knowledge into a mechanism of oxidative water splitting with special emphasis on the formation of the essential O-O bond and on the active role of the protein in tuning the local proton activity that depends on time and redox state Si. The O-O linkage is assumed to take place at the level of a complexed peroxide.
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Affiliation(s)
- Gernot Renger
- Technische Universität Berlin, Institut für Chemie, Max-Volmer-Laboratorium für Biophysikalische Chemie, Strasse des 17. Juni 135, D-10623 Berlin, Germany.
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42
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Krivanek R, Kern J, Zouni A, Dau H, Haumann M. Spare quinones in the QB cavity of crystallized photosystem II from Thermosynechococcus elongatus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:520-7. [PMID: 17397795 DOI: 10.1016/j.bbabio.2007.02.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Revised: 02/13/2007] [Accepted: 02/19/2007] [Indexed: 11/25/2022]
Abstract
The recent crystallographic structure at 3.0 A resolution of PSII from Thermosynechococcus elongatus has revealed a cavity in the protein which connects the membrane phase to the binding pocket of the secondary plastoquinone Q(B). The cavity may serve as a quinone diffusion pathway. By fluorescence methods, electron transfer at the donor and acceptor sides was investigated in the same membrane-free PSII core particle preparation from T. elongatus prior to and after crystallization; PSII membrane fragments from spinach were studied as a reference. The data suggest selective enrichment of those PSII centers in the crystal that are intact with respect to O(2) evolution at the manganese-calcium complex of water oxidation and with respect to the integrity of the quinone binding site. One and more functional quinone molecules (per PSII monomer) besides of Q(A) and Q(B) were found in the crystallized PSII. We propose that the extra quinones are located in the Q(B) cavity and serve as a PSII intrinsic pool of electron acceptors.
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Affiliation(s)
- Roland Krivanek
- Freie Universität Berlin, FB Physik, Arnimallee 14, D-14195 Berlin, Germany
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Cooper IB, Barry BA. Perturbations at the chloride site during the photosynthetic oxygen-evolving cycle. PHOTOSYNTHESIS RESEARCH 2007; 92:345-56. [PMID: 17375370 DOI: 10.1007/s11120-007-9147-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Accepted: 02/08/2007] [Indexed: 05/14/2023]
Abstract
Photosystem II (PSII) catalyzes the oxidation of water to O2 at the manganese-containing, oxygen-evolving complex (OEC). Photoexcitation of PSII results in the oxidation of the OEC; four sequential oxidation reactions are required for the generation and release of molecular oxygen. Therefore, with flash illumination, the OEC cycles among five Sn states. Chloride depletion inhibits O2 evolution. However, the binding site of chloride in the OEC is not known, and the role of chloride in oxygen evolution has not as yet been elucidated. We have employed reaction-induced FT-IR spectroscopy and selective flash excitation, which cycles PSII samples through the S state transitions. On the time scale employed, these FT-IR difference spectra reflect long-lived structural changes in the OEC. Bromide substitution supports oxygen evolution and was used to identify vibrational bands arising from structural changes at the chloride-binding site. Contributions to the vibrational spectrum from bromide-sensitive bands were observed on each flash. Sulfate treatment led to an elimination of oxygen evolution activity and of the FT-IR spectra assigned to the S3 to S0 (third flash) and S0 to S1 transitions (fourth flash). However, sulfate treatment changed, but did not eliminate, the FT-IR spectra obtained with the first and second flashes. Solvent isotope exchange in chloride-exchanged samples suggests flash-dependent structural changes, which alter protein dynamics during the S state cycle.
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Affiliation(s)
- Ian B Cooper
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
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Buchta J, Grabolle M, Dau H. Photosynthetic dioxygen formation studied by time-resolved delayed fluorescence measurements--method, rationale, and results on the activation energy of dioxygen formation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:565-74. [PMID: 17543884 DOI: 10.1016/j.bbabio.2007.04.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 03/30/2007] [Accepted: 04/16/2007] [Indexed: 11/22/2022]
Abstract
The analysis of the time-resolved delayed fluorescence (DF) measurements represents an important tool to study quantitatively light-induced electron transfer as well as associated processes, e.g. proton movements, at the donor side of photosystem II (PSII). This method can provide, inter alia, insights in the functionally important inner-protein proton movements, which are hardly detectable by conventional spectroscopic approaches. The underlying rationale and experimental details of the method are described. The delayed emission of chlorophyll fluorescence of highly active PSII membrane particles was measured in the time domain from 10 mus to 60 ms after each flash of a train of nanosecond laser pulses. Focusing on the oxygen-formation step induced by the third flash, we find that the recently reported formation of an S4-intermediate prior to the onset of O-O bond formation [M. Haumann, P. Liebisch, C. Müller, M. Barra, M. Grabolle, H. Dau, Science 310, 1019-1021, 2006] is a multiphasic process, as anticipated for proton movements from the manganese complex of PSII to the aqueous bulk phase. The S4-formation involves three or more likely sequential steps; a tri-exponential fit yields time constants of 14, 65, and 200 mus (at 20 degrees C, pH 6.4). We determine that S4-formation is characterized by a sizable difference in Gibbs free energy of more than 90 meV (20 degrees C, pH 6.4). In the second part of the study, the temperature dependence (-2.7 to 27.5 degrees C) of the rate constant of dioxygen formation (600/s at 20 degrees C) was investigated by analysis of DF transients. If the activation energy is assumed to be temperature-independent, a value of 230 meV is determined. There are weak indications for a biphasicity in the Arrhenius plot, but clear-cut evidence for a temperature-dependent switch between two activation energies, which would point to the existence of two distinct rate-limiting steps, is not obtained.
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Affiliation(s)
- Joachim Buchta
- Freie University Berlin, FB Physik, Arnimallee 14, D-14195 Berlin, Germany
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Renger G, Kühn P. Reaction pattern and mechanism of light induced oxidative water splitting in photosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1767:458-71. [PMID: 17428439 DOI: 10.1016/j.bbabio.2006.12.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2006] [Revised: 12/08/2006] [Accepted: 12/13/2006] [Indexed: 11/18/2022]
Abstract
This mini review is an attempt to briefly summarize our current knowledge on light driven oxidative water splitting in photosynthesis. The reaction leading to molecular oxygen and four protons via photosynthesis comprises thermodynamic and kinetic constraints that require a balanced fine tuning of the reaction coordinates. The mode of coupling between electron (ET) and proton transfer (PT) reactions is shown to be of key mechanistic relevance for the redox turnover of Y(Z) and the reactions within the WOC. The WOC is characterized by peculiar energetics of its oxidation steps in the WOC. In all oxygen evolving photosynthetic organisms the redox state S(1) is thermodynamically most stable and therefore this general feature is assumed to be of physiological relevance. Available information on the Gibbs energy differences between the individual redox states S(i+1) and S(i) and on the activation energies of their oxidative transitions are used to construct a general reaction coordinate of oxidative water splitting in photosystem II (PS II). Finally, an attempt is presented to cast our current state of knowledge into a mechanism of oxidative water splitting with special emphasis on the formation of the essential O-O bond and the active role of the protein environment in tuning the local proton activity that depends on time and redox state S(i). The O-O linkage is assumed to take place within a multistate equilibrium at the redox level of S(3), comprising both redox isomerism and proton tautomerism. It is proposed that one state, S(3)(P), attains an electronic configuration and nuclear geometry that corresponds with a hydrogen bonded peroxide which acts as the entatic state for the generation of complexed molecular oxygen through S(3)(P) oxidation by Y(Z)(ox).
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Affiliation(s)
- Gernot Renger
- Technische Universität Berlin, Institut für Chemie, Max-Volmer-Laboratorium für Biophysikalische Chemie, Strasse des 17.Juni 135, D-10623 Berlin, Germany.
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