1
|
Determining the Electronic Structure of Paramagnetic Intermediates in membrane proteins: A high-resolution 2D 1H hyperfine sublevel correlation study of the redox-active tyrosines of photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183422. [DOI: 10.1016/j.bbamem.2020.183422] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 06/19/2020] [Accepted: 07/15/2020] [Indexed: 01/26/2023]
|
2
|
Shimada Y, Kitajima-Ihara T, Nagao R, Noguchi T. Role of the O4 Channel in Photosynthetic Water Oxidation as Revealed by Fourier Transform Infrared Difference and Time-Resolved Infrared Analysis of the D1-S169A Mutant. J Phys Chem B 2020; 124:1470-1480. [DOI: 10.1021/acs.jpcb.9b11946] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Yuichiro Shimada
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Tomomi Kitajima-Ihara
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Ryo Nagao
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takumi Noguchi
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| |
Collapse
|
3
|
Shimizu T, Sugiura M, Noguchi T. Mechanism of Proton-Coupled Electron Transfer in the S0-to-S1 Transition of Photosynthetic Water Oxidation As Revealed by Time-Resolved Infrared Spectroscopy. J Phys Chem B 2018; 122:9460-9470. [DOI: 10.1021/acs.jpcb.8b07455] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Tatsuki Shimizu
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Miwa Sugiura
- Proteo-Science Research Center, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Takumi Noguchi
- Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| |
Collapse
|
4
|
Sakamoto H, Shimizu T, Nagao R, Noguchi T. Monitoring the Reaction Process During the S2 → S3 Transition in Photosynthetic Water Oxidation Using Time-Resolved Infrared Spectroscopy. J Am Chem Soc 2017; 139:2022-2029. [DOI: 10.1021/jacs.6b11989] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Hiroki Sakamoto
- Division of Material Science,
Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Tatsuki Shimizu
- Division of Material Science,
Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Ryo Nagao
- Division of Material Science,
Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takumi Noguchi
- Division of Material Science,
Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| |
Collapse
|
5
|
Renger G. Mechanism of light induced water splitting in Photosystem II of oxygen evolving photosynthetic organisms. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1164-76. [PMID: 22353626 DOI: 10.1016/j.bbabio.2012.02.005] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 01/27/2012] [Accepted: 02/05/2012] [Indexed: 11/24/2022]
Abstract
The reactions of light induced oxidative water splitting were analyzed within the framework of the empirical rate constant-distance relationship of non-adiabatic electron transfer in biological systems (C. C. Page, C. C. Moser, X. Chen , P. L. Dutton, Nature 402 (1999) 47-52) on the basis of structure information on Photosystem II (PS II) (A. Guskov, A. Gabdulkhakov, M. Broser, C. Glöckner, J. Hellmich, J. Kern, J. Frank, W. Saenger, A. Zouni, Chem. Phys. Chem. 11 (2010) 1160-1171, Y. Umena, K. Kawakami, J-R Shen, N. Kamiya, Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9Å. Nature 47 (2011) 55-60). Comparison of these results with experimental data leads to the following conclusions: 1) The oxidation of tyrosine Y(z) by the cation radical P680(+·) in systems with an intact water oxidizing complex (WOC) is kinetically limited by the non-adiabatic electron transfer step and the extent of this reaction is thermodynamically determined by relaxation processes in the environment including rearrangements of hydrogen bond network(s). In marked contrast, all Y(z)(ox) induced oxidation steps in the WOC up to redox state S(3) are kinetically limited by trigger reactions which are slower by orders of magnitude than the rates calculated for non-adiabatic electron transfer. 3) The overall rate of the triggered reaction sequence of Y(z)(ox) reduction by the WOC in redox state S(3) eventually leading to formation and release of O(2) is kinetically limited by an uphill electron transfer step. Alternative models are discussed for this reaction. The protein matrix of the WOC and bound water molecules provide an optimized dynamic landscape of hydrogen bonded protons for catalyzing oxidative water splitting energetically driven by light induced formation of the cation radical P680(+·). In this way the PS II core acts as a molecular machine formed during a long evolutionary process. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.
Collapse
|
6
|
Barry BA. Proton coupled electron transfer and redox active tyrosines in Photosystem II. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2011; 104:60-71. [PMID: 21419640 PMCID: PMC3164834 DOI: 10.1016/j.jphotobiol.2011.01.026] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 01/25/2011] [Accepted: 01/31/2011] [Indexed: 11/30/2022]
Abstract
In this article, progress in understanding proton coupled electron transfer (PCET) in Photosystem II is reviewed. Changes in acidity/basicity may accompany oxidation/reduction reactions in biological catalysis. Alterations in the proton transfer pathway can then be used to alter the rates of the electron transfer reactions. Studies of the bioenergetic complexes have played a central role in advancing our understanding of PCET. Because oxidation of the tyrosine results in deprotonation of the phenolic oxygen, redox active tyrosines are involved in PCET reactions in several enzymes. This review focuses on PCET involving the redox active tyrosines in Photosystem II. Photosystem II catalyzes the light-driven oxidation of water and reduction of plastoquinone. Photosystem II provides a paradigm for the study of redox active tyrosines, because this photosynthetic reaction center contains two tyrosines with different roles in catalysis. The tyrosines, YZ and YD, exhibit differences in kinetics and midpoint potentials, and these differences may be due to noncovalent interactions with the protein environment. Here, studies of YD and YZ and relevant model compounds are described.
Collapse
Affiliation(s)
- Bridgette A Barry
- School of Chemistry and Biochemistry and The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA.
| |
Collapse
|
7
|
Gerencsér L, Dau H. Water Oxidation by Photosystem II: H2O−D2O Exchange and the Influence of pH Support Formation of an Intermediate by Removal of a Proton before Dioxygen Creation. Biochemistry 2010; 49:10098-106. [DOI: 10.1021/bi101198n] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- László Gerencsér
- Freie Universität Berlin, FB Physik, Arnimallee 14, D-14195 Berlin, Germany
| | - Holger Dau
- Freie Universität Berlin, FB Physik, Arnimallee 14, D-14195 Berlin, Germany
| |
Collapse
|
8
|
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.
Collapse
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.
| |
Collapse
|
9
|
Affiliation(s)
- James P McEvoy
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA
| | | |
Collapse
|
10
|
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).
Collapse
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.
| | | |
Collapse
|
11
|
Renger G. Coupling of electron and proton transfer in oxidative water cleavage in photosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1655:195-204. [PMID: 15100032 DOI: 10.1016/j.bbabio.2003.07.007] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2003] [Revised: 07/23/2003] [Accepted: 07/23/2003] [Indexed: 11/29/2022]
Abstract
This minireview addresses questions on the mechanism of oxidative water cleavage with special emphasis on the coupling of electron (ET) and proton transfer (PT) of each individual redox step of the reaction sequence and on the mode of O-O bond formation. The following topics are discussed: (1) the multiphasic kinetics of Y(Z)(ox) formation by P680(+*) originate from three different types of rate limitations: (i) nonadiabatic electron transfer for the "fast" ns reaction, (ii) local "dielectric" relaxation for the "slow" ns reaction, and (iii) "large-scale" proton shift for the micros kinetics; (2) the ET/PT-coupling mode of the individual redox transitions within the water oxidizing complex (WOC) driven by Y(Z)(ox) is assumed to depend on the redox state S(i): the oxidation steps of S(0) and S(1) comprise separate ET and PT pathways while those of S(2) and S(3) take place via proton-coupled electron transfer (PCET) analogous to Jerry Babcock's hydrogen atom abstractor model [Biochim. Biophys. Acta, 1458 (2000) 199]; (3) S(3) is postulated to be a multistate redox level of the WOC with fast dynamic equilibria of both redox isomerism and proton tautomerism. The primary event in the essential O-O bond formation is the population of a state S(3)(P) characterized by an electronic configuration and nuclear geometry that corresponds with a complexed hydrogen peroxide; (4) the peroxidic type S(3)(P) is the entatic state for formation of complexed molecular oxygen through S(3) oxidation by Y(Z)(ox); and (5) the protein matrix itself is proposed to exert catalytic activity by functioning as "PCET director". The WOC is envisaged as a supermolecule that is especially tailored for oxidative water cleavage and acts as a molecular machine.
Collapse
Affiliation(s)
- G Renger
- Max-Volmer-Laboratory of the Institute of Chemistry, Technical University Berlin, PC 14, Strasse des 17 Juni 135, D-10623 Berlin, Germany.
| |
Collapse
|
12
|
McEvoy JP, Brudvig GW. Structure-based mechanism of photosynthetic water oxidation. Phys Chem Chem Phys 2004. [DOI: 10.1039/b407500e] [Citation(s) in RCA: 174] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
13
|
Chroni S, Ghanotakis DF. Accessibility of tyrosine Y(.)(Z) to exogenous reductants and Mn(2+) in various Photosystem II preparations. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1504:432-7. [PMID: 11245806 DOI: 10.1016/s0005-2728(01)00159-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reduction of tyrosine Y(.)(Z) by benzidine and exogenous Mn(2+) was studied by kinetic EPR experiments in various Photosystem II (PSII) preparations. Using lanthanide treated PSII membranes it was demonstrated that neither the extrinsic polypeptides (17, 23 and 33 kDa) nor the Mn complex block the accessibility of Y(.)(Z) to exogenous reductants, such as benzidine. In addition, it was shown that in the presence of the native Mn complex exogenous Mn(2+) does not reduce Y(.)(Z).
Collapse
Affiliation(s)
- S Chroni
- Department of Chemistry, University of Crete, PO Box 1470, 71409 Heraklion, Crete, Greece
| | | |
Collapse
|
14
|
Renger G. Photosynthetic water oxidation to molecular oxygen: apparatus and mechanism. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1503:210-28. [PMID: 11115635 DOI: 10.1016/s0005-2728(00)00227-9] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- G Renger
- Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623, Berlin, Germany.
| |
Collapse
|
15
|
Westphal KL, Lydakis-Simantiris N, Cukier RI, Babcock GT. Effects of Sr2+-substitution on the reduction rates of Yz* in PSII membranes--evidence for concerted hydrogen-atom transfer in oxygen evolution. Biochemistry 2000; 39:16220-9. [PMID: 11123952 DOI: 10.1021/bi0018077] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several groups have recently investigated the kinetic effects of biochemical treatments, site-directed mutagenesis, or substitution of essential cofactors on the stepwise, water-oxidizing chemistry catalyzed by Photosystem II. Consistently, these studies show evidence for a slowing of the final, oxygen-releasing step, S(3) --> S(0), of the catalytic cycle. To a degree, some of this work also shows a slowing of the earlier S-state transitions. To study these processes in more detail, we have investigated the effect of replacing Ca(2+) with Sr(2+)on the rates of the S-state transitions by using time-resolved electron paramagnetic resonance. The results show a slowdown of the last transition in the cycle, consistent with a report from Boussac et al. [Boussac, A., Sétif, P., and Rutherford, A. W. (1992) Biochemistry 31, 1224-1234], and of the earlier S-state transitions as well, which suggests that a common molecular mechanism is at work and that Sr(2+) is less effective than Ca(2+) in supporting it. While the oxidation of Y(z) by P(680)(+) has been extensively studied and can be understood within the context of nonadiabatic electron tunneling combined with rapid, non-rate-limiting proton transfer in the holo-system [Tommos, C., and Babcock, G. T. (2000) Biochim. Biophys. Acta 1458, 199], the reduction of Y(z*) by the Mn cluster cannot be described effectively by a nonadiabatic electron-transfer formalism. This indicates that this reaction is rate limited by processes other than electron tunneling. We discuss our results for Y(z*) reduction and those of others for the activation parameters (E(a), A, KIE, and rates) associated with this process, in terms of both sequential and concerted proton-coupled, electron transfer. Our analysis indicates that concerted hydrogen-atom transfer processes best explain the observed characteristics of the S-state advances.
Collapse
Affiliation(s)
- K L Westphal
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | | | | | | |
Collapse
|
16
|
Hutchison RS, Steenhuis JJ, Yocum CF, Razeghifard MR, Barry BA. Deprotonation of the 33-kDa, extrinsic, manganese-stabilizing subunit accompanies photooxidation of manganese in photosystem II. J Biol Chem 1999; 274:31987-95. [PMID: 10542229 DOI: 10.1074/jbc.274.45.31987] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Photosystem II catalyzes photosynthetic water oxidation. The oxidation of water to molecular oxygen requires four sequential oxidations; the sequentially oxidized forms of the catalytic site are called the S states. An extrinsic subunit, the manganese-stabilizing protein (MSP), promotes the efficient turnover of the S states. MSP can be removed and rebound to the reaction center; removal and reconstitution is associated with a decrease in and then a restoration of enzymatic activity. We have isotopically edited MSP by uniform (13)C labeling of the Escherichia coli-expressed protein and have obtained the Fourier transform infrared spectrum associated with the S(1) to S(2) transition in the presence either of reconstituted (12)C or (13)C MSP. (13)C labeling of MSP is shown to cause 30-60 cm(-1) shifts in a subset of vibrational lines. The derived, isotope-edited vibrational spectrum is consistent with a deprotonation of glutamic/aspartic acid residues on MSP during the S(1) to S(2) transition; the base, which accepts this proton(s), is not located on MSP. This finding suggests that this subunit plays a role as a stabilizer of a charged transition state and, perhaps, as a general acid/base catalyst of oxygen evolution. These results provide a molecular explanation for known MSP effects on oxygen evolution.
Collapse
Affiliation(s)
- R S Hutchison
- Department of Biochemistry, University of Minnesota, St. Paul, Minnesota 55108, USA
| | | | | | | | | |
Collapse
|
17
|
Rousset M, Montet Y, Guigliarelli B, Forget N, Asso M, Bertrand P, Fontecilla-Camps JC, Hatchikian EC. [3Fe-4S] to [4Fe-4S] cluster conversion in Desulfovibrio fructosovorans [NiFe] hydrogenase by site-directed mutagenesis. Proc Natl Acad Sci U S A 1998; 95:11625-30. [PMID: 9751716 PMCID: PMC21691 DOI: 10.1073/pnas.95.20.11625] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The role of the high potential [3Fe-4S]1+,0 cluster of [NiFe] hydrogenase from Desulfovibrio species located halfway between the proximal and distal low potential [4Fe-4S]2+,1+ clusters has been investigated by using site-directed mutagenesis. Proline 238 of Desulfovibrio fructosovorans [NiFe] hydrogenase, which occupies the position of a potential ligand of the lacking fourth Fe-site of the [3Fe-4S] cluster, was replaced by a cysteine residue. The properties of the mutant enzyme were investigated in terms of enzymatic activity, EPR, and redox properties of the iron-sulfur centers and crystallographic structure. We have shown on the basis of both spectroscopic and x-ray crystallographic studies that the [3Fe-4S] cluster of D. fructosovorans hydrogenase was converted into a [4Fe-4S] center in the P238 mutant. The [3Fe-4S] to [4Fe-4S] cluster conversion resulted in a lowering of approximately 300 mV of the midpoint potential of the modified cluster, whereas no significant alteration of the spectroscopic and redox properties of the two native [4Fe-4S] clusters and the NiFe center occurred. The significant decrease of the midpoint potential of the intermediate Fe-S cluster had only a slight effect on the catalytic activity of the P238C mutant as compared with the wild-type enzyme. The implications of the results for the role of the high-potential [3Fe-4S] cluster in the intramolecular electron transfer pathway are discussed.
Collapse
Affiliation(s)
- M Rousset
- Unité de Bioénergétique et Ingéniérie des Protéines, Institut de Biologie Structurale et Microbiologie, Centre National de la Recherche Scientifique, 31, Chemin Joseph Aiguier, 13402 Marseille CDX 20, France
| | | | | | | | | | | | | | | |
Collapse
|
18
|
Tommos C, Hoganson CW, Valentin MD, Lydakis-Simantiris N, Dorlet P, Westphal K, Chu HA, McCracken J, Babcock GT. Manganese and tyrosyl radical function in photosynthetic oxygen evolution. Curr Opin Chem Biol 1998; 2:244-52. [PMID: 9667938 DOI: 10.1016/s1367-5931(98)80066-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Photosystem II catalyzes the photosynthetic oxidation of water to O2. The structural and functional basis for this remarkable process is emerging. The catalytic site contains a tetramanganese cluster, calcium, chloride and a redox-active tyrosine organized so as to promote electroneutral hydrogen atom abstraction from manganese-bound substrate water by the tyrosyl radical. Recent work is assessed within the framework of this model for the water oxidizing process.
Collapse
Affiliation(s)
- C Tommos
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | | | | | | | | | | | | | | | | |
Collapse
|