Affiliation:
1. Department of Chemistry, Yale University, PO Box 208107, New Haven, CT 06520–8107, USA
Abstract
The O
2
–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 O
2
evolution are discussed. Emphasis is given to the proton–coupled electron–transfer steps involved in oxidation of the manganese cluster by oxidized tyrosine Z (Y
Z
), the function of Ca
2+
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 O
2
evolution is presented in which the O–O bond–forming step occurs via nucleophilic attack on an electron–deficient Mn
V
=O species by a calcium–bound water molecule. The proposed mechanism includes specific roles for the tetranuclear manganese cluster, calcium, chloride, Y
Z
and His190 of the D1 polypeptide. Recent studies of the ion selectivity of the calcium site in the O
2
–evolving complex and of a functional inorganic manganese model system that test key aspects of this mechanism are also discussed.
Subject
General Agricultural and Biological Sciences,General Biochemistry, Genetics and Molecular Biology
Cited by
51 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献