Effect of reversible extraction of manganese on photooxidation of chlorophyll P680 in Photosystem II preparations

Abstract

Effect of reversible extraction of Mn on the amplitude of photoinduced absorbance changes (ΔA) related to photooxidation of chlorophyll P 680 in pea oxygen-evolving Photosystem II (PS II) preparations has been studied. It is shown that complete removal of Mn results in a 7-8-fold increase of the ΔA amplitude which is decreased again to the initial value upon subsequent addition of MnCl 2 . This reactivation needs 4 Mn atoms per reaction center (RC) of PS II. In the presence of 3 μM MgCl 2 the reactivation requires two Mn atoms per 1 RC of PS II. The obtained data confirm our earlier conclusion (Klimov V.V., S.I. Allakhverdiev, V.A. Shuvalov and A.A. Krasnovsky (1982) FEBS Lett. 148, 307-312) that a four-atomic Mn center functions on t he donor side of PS II; two of the atoms can be replaced by either Mg 2+ or another bivalent metal.