A New 4.8-kDa Polypeptide Intrinsic to the PS II Reaction Center, as Revealed by Modified SDS-PAGE with Improved Resolution of Low-Molecular-Weight Proteins

摘要

Low-molecular-weight polypeptides in various PS II preparations from spinach and wheat were analyzed by modified SDS-PAGE, which gave good resolution of low-molecular-weight proteins with minimized interference by lipids. PS II membrane fragments contained at least nine low-molecular-weight polypeptides of between 3.9 kDa and 11 kDa, and all of them were identified in thylakoid membranes. Of these nine polypeptides, the 10-kDa phosphoprotein, the 5-kDa, 4.8-kDa, and 4.1-kDa polypeptides, and the two subunits of cytochrome b559were commonly found in O2-evolving core complexes of wheat and spinach. In contrast, PS II reaction center complexes that consisted of D1, D2 and two cytochrome b559polypeptides retained only the 4.8- kDa polypeptide. Analysis by Western blotting revealed that the 4.8-kDa polypeptide is an intrinsic component of the PS II reaction center.