Requirements for the photoligation of Mn2+ in PS II membranes and the expression of water‐oxidizing activity of the polynuclear Mn‐catalyst

Abstract

Ligation of Mn²⁺ into the polynuclear Mn‐catalyst of water oxidation was shown using PS II membranes depleted of their Mn and the 17, 23 and 33 kDa extrinsic proteins. This process specifically required light and Ca²⁺ concentrations of 5̃0 mM. Evidence was obtained indicating Mn²⁺/Ca²⁺ competition for Ca²⁺ and Mn²⁺ binding sites essential for the photoligation of Mn. Photoligation of Mn did not result in an increase of water oxidation capacity; however, water oxidation capacity was expressed following dark reconstitution minimally with the 33 kDa protein. The results represent the first observation of photoactivation of water oxidation in a system that excludes simple light‐driven Mn²⁺ transport across membrane(s).