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Issue 20, 2004
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Structure-based mechanism of photosynthetic water oxidation

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The recently-published 3.5 Å resolution X-ray crystal structure of a cyanobacterial photosystem II (PDB entry 1S5L) provides a detailed architecture of the oxygen-evolving complex (OEC) and the surrounding amino-acids [K. N. Ferreira, T. M. Iverson, K. Maghlaoui, J. Barber and S. Iwata, Science, 2004, 203, 1831–1838]. The revealed geometry of the OEC lends weight to certain hypothesized mechanisms for water-splitting, including the one propounded by this group, in which a calcium-bound water acts as a nucleophile to attack the oxygen of a MnV[double bond, length as m-dash]O group in the crucial O–O bond-forming step [J. S. Vrettos, J. Limburg and G. W. Brudvig, Biochim. Biophys. Acta, 2001, 1503, 229–245]. Here we re-examine this mechanism in the light of the new crystallographic information and make detailed suggestions concerning the mechanistic functions (especially the redox and proton-transfer roles) of calcium, chloride and certain amino-acid residues in and around the OEC. In particular, we propose an important role for an arginine residue, CP43–Arg357, in abstracting protons from a substrate water molecule during the water-splitting reaction.

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Publication details

The article was received on 18 May 2004, accepted on 09 Jul 2004 and first published on 19 Jul 2004

Article type: Paper
DOI: 10.1039/B407500E
Citation: Phys. Chem. Chem. Phys., 2004,6, 4754-4763
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    Structure-based mechanism of photosynthetic water oxidation

    J. P. McEvoy and G. W. Brudvig, Phys. Chem. Chem. Phys., 2004, 6, 4754
    DOI: 10.1039/B407500E

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