Removal of the 33 kDa extrinsic protein from photosystem (PS) II membranes resulted in markedly increased stabilization of the S2QA − charge pair as measured by thermoluminescence. The stabilization increase was specific for the S2QA − charge pair and did not require any special herbicide. The effect was fully reversed by reconstitution with the 33 kDa protein, but not at all by high concentrations of Cl−, as opposed to those effects known to be reversed by 200 mM Cl− . The data are interpreted as indicating a structural change of the donor and/or acceptor side of PS II dependent on association with the 33 kDa extrinsic protein.
