Water oxidation in PSII - H atom abstraction revisited

Ron J. Pace; Karin A. Åhrling

doi:10.1016/j.bbabio.2003.09.016

Water oxidation in PSII - H atom abstraction revisited

Ron J. Pace^*, Karin A. Åhrling

^*Corresponding author for this work

Research output: Contribution to journal › Review article › peer-review

19 Citations (Scopus)

Abstract

A model for the water oxidation reaction in Photosystem II (PSII) is presented, based on an H atom abstraction mechanism. The model rationalises the S-state dependence of observed substrate water exchange kinetics [Biochim. Biophys. Acta 1503 (2001) 197] and assumes that H transfer occurs to an oxidised μ-oxo bridge oxygen on the S₃→S₄→S ₀ transition. The model requires that only one Mn-pair and a Ca ion be directly involved in the substrate binding and catalytic function. The multiline signal observed in the S₀ state is shown to plausibly arise from such a system. A detailed molecular model of the three-metal site, assuming ligation by those residues identified by mutagenesis as Ca/Mn ligands is presented. This bears a resemblance to the dinuclear Mn site in Mn catalase and is generally consistent with the electron density map of cyanobacterial PSII recently presented [Proc. Natl. Acad. Sci. U. S. A. 100 (2003) 98].

Original language	English
Pages (from-to)	172-178
Number of pages	7
Journal	Biochimica et Biophysica Acta - Bioenergetics
Volume	1655
Issue number	1-3
DOIs	https://doi.org/10.1016/j.bbabio.2003.09.016
Publication status	Published - 12 Apr 2004

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title = "Water oxidation in PSII - H atom abstraction revisited",

abstract = "A model for the water oxidation reaction in Photosystem II (PSII) is presented, based on an H atom abstraction mechanism. The model rationalises the S-state dependence of observed substrate water exchange kinetics [Biochim. Biophys. Acta 1503 (2001) 197] and assumes that H transfer occurs to an oxidised μ-oxo bridge oxygen on the S3→S4→S 0 transition. The model requires that only one Mn-pair and a Ca ion be directly involved in the substrate binding and catalytic function. The multiline signal observed in the S0 state is shown to plausibly arise from such a system. A detailed molecular model of the three-metal site, assuming ligation by those residues identified by mutagenesis as Ca/Mn ligands is presented. This bears a resemblance to the dinuclear Mn site in Mn catalase and is generally consistent with the electron density map of cyanobacterial PSII recently presented [Proc. Natl. Acad. Sci. U. S. A. 100 (2003) 98].",

keywords = "EPR, EXAFS, Extended X-ray absorption fine structure, H atom abstraction, MeOH, Methanol, Mn cluster, PSII, Photosystem II, WOC, Water oxidising complex, X-ray absorption near edge spectroscopy, XANES",

author = "Pace, {Ron J.} and {\AA}hrling, {Karin A.}",

year = "2004",

month = apr,

day = "12",

doi = "10.1016/j.bbabio.2003.09.016",

language = "English",

volume = "1655",

pages = "172--178",

journal = "Biochimica et Biophysica Acta - Bioenergetics",

issn = "0005-2728",

publisher = "Elsevier B.V.",

number = "1-3",

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TY - JOUR

T1 - Water oxidation in PSII - H atom abstraction revisited

AU - Pace, Ron J.

AU - Åhrling, Karin A.

PY - 2004/4/12

Y1 - 2004/4/12

N2 - A model for the water oxidation reaction in Photosystem II (PSII) is presented, based on an H atom abstraction mechanism. The model rationalises the S-state dependence of observed substrate water exchange kinetics [Biochim. Biophys. Acta 1503 (2001) 197] and assumes that H transfer occurs to an oxidised μ-oxo bridge oxygen on the S3→S4→S 0 transition. The model requires that only one Mn-pair and a Ca ion be directly involved in the substrate binding and catalytic function. The multiline signal observed in the S0 state is shown to plausibly arise from such a system. A detailed molecular model of the three-metal site, assuming ligation by those residues identified by mutagenesis as Ca/Mn ligands is presented. This bears a resemblance to the dinuclear Mn site in Mn catalase and is generally consistent with the electron density map of cyanobacterial PSII recently presented [Proc. Natl. Acad. Sci. U. S. A. 100 (2003) 98].

AB - A model for the water oxidation reaction in Photosystem II (PSII) is presented, based on an H atom abstraction mechanism. The model rationalises the S-state dependence of observed substrate water exchange kinetics [Biochim. Biophys. Acta 1503 (2001) 197] and assumes that H transfer occurs to an oxidised μ-oxo bridge oxygen on the S3→S4→S 0 transition. The model requires that only one Mn-pair and a Ca ion be directly involved in the substrate binding and catalytic function. The multiline signal observed in the S0 state is shown to plausibly arise from such a system. A detailed molecular model of the three-metal site, assuming ligation by those residues identified by mutagenesis as Ca/Mn ligands is presented. This bears a resemblance to the dinuclear Mn site in Mn catalase and is generally consistent with the electron density map of cyanobacterial PSII recently presented [Proc. Natl. Acad. Sci. U. S. A. 100 (2003) 98].

KW - EPR

KW - EXAFS

KW - Extended X-ray absorption fine structure

KW - H atom abstraction

KW - MeOH

KW - Methanol

KW - Mn cluster

KW - PSII

KW - Photosystem II

KW - WOC

KW - Water oxidising complex

KW - X-ray absorption near edge spectroscopy

KW - XANES

UR - http://www.scopus.com/inward/record.url?scp=1942472548&partnerID=8YFLogxK

U2 - 10.1016/j.bbabio.2003.09.016

DO - 10.1016/j.bbabio.2003.09.016

M3 - Review article

SN - 0005-2728

VL - 1655

SP - 172

EP - 178

JO - Biochimica et Biophysica Acta - Bioenergetics

JF - Biochimica et Biophysica Acta - Bioenergetics

IS - 1-3

ER -

Water oxidation in PSII - H atom abstraction revisited

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