Water oxidation chemistry of photosystem II

John S. Vrettos, Gary W. Brudvig, C. Dismukes, L. Hammarström, W. Junge, P. E.M. Siegbahn, J. De Las Rivas

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


The O2-evolving complex of photosystem II catalyses the light-driven four-electron oxidation of water to dioxygen in photosynthesis. In this article, the steps leading to photosynthetic O2 evolution are discussed. Emphasis is given to the proton-coupled electron-transfer steps involved in oxidation of the manganese cluster by oxidized tyrosine Z (YZ·), the function of Ca2+ and the mechanism by which water is activated for formation of an O-O bond. Based on a consideration of the biophysical studies of photosystem II and inorganic manganese model chemistry, a mechanism for photosynthetic O2 evolution is presented in which the O-O bond-forming step occurs via nucleophilic attack on an electron-deficient MnV=O species by a calcium-bound water molecule. The proposed mechanism includes specific roles for the tetranuclear manganese cluster, calcium, chloride, YZ and His190 of the D1 polypeptide. Recent studies of the ion selectivity of the calcium site in the O2-evolving complex and of a functional inorganic manganese model system that test key aspects of this mechanism are also discussed.

Original languageEnglish
Pages (from-to)1395-1405
Number of pages11
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Issue number1426
Publication statusPublished - Oct 29 2002


  • Calcium
  • Chloride
  • Manganese
  • Oxygen-evolving complex
  • Photosystem II
  • Tyrosyl radical

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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