THE INTRINSIC 22 KDA PROTEIN IS A CHLOROPHYLL-BINDING SUBUNIT OF PHOTOSYSTEM-II

The intrinsic 22 kDa polypeptide associated with photosystem II (psbS protein) was found to be able to bind chlorophyll. Extraction of isola ted photosystem II membranes with octyl-thioglucopyranoside, followed by repetitive electrophoresis under partially denaturing conditions ga ve only one green band. It contained both chlorophyll a and chlorophyl l b, exhibited an absorption maximum at 674 nm and a 77 K fluorescence peak at 675 Mn. The chIorophyll-protein band contained a single polyp eptide of 22 kDa. Based on these results and on previous protein seque nce comparisons, it is suggested that the psbS protein is a chlorophyl l a/b binding polypeptide and should thus be denoted CP22.