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.