Regulation of photo-induced cross-linking of the D1 protein and CP43 in PSII by ATP

Abstract

One of the remarkable phenomena in photoinhibition of PS II is generation of cross-linked products between the D1 protein and the nearby polypeptides in PS II and the following digestion of these products by a stromal protease(s). When spinach PS II membranes that had been treated with 0.8 M Tris (pH 9.0) were illuminated with strong light, more than 30% of the total D1 protein appeared as cross-linked products. By studying the details of the related processes, we concluded that the D1 cross-linking and degradation of the cross-linked products comprise a novel pathway of the D1 turnover. In the present study, we found that the light-induced D1 cross-linking is suppressed completely by the addition of ATP to the PSII membranes. The cross-linking was stimulated when ATP was omitted and the endogenous ATP was hydrolyzed by the addition of apyrase in the reaction mixture before the illumination. These results suggest that the cross-linking of the D1 protein and CP43 is dependent not only on the photooxidation of amino acids in the both proteins, but also on the conformation of the proteins probably determined by the phosphorylation/dephosphorylation conditions.