EPR characteristics of chloride-depleted photosystem II membranes in the presence of other anions

Abstract

Chloride is an essential cofactor for the oxidation of water to oxygen. Anion substitution (Br⁻, I⁻, NO₂⁻, F⁻) in Cl⁻-depleted PS II membranes brings out significant changes in the EPR signals arising from the S₂ state and from the iron–quinone complex of PS II. On the basis of the changes observed in the S₂ state multiline signal and the Q_AFe³⁺ EPR signal in Cl⁻-depleted PS II membranes after substituting with various anions, we report a possible binding site of anions such as chloride and bromide at the PS II donor side as well as at the acceptor side.