Immunological characterization of photosystem II chlorophyll-binding proteins from the cyanobacterium, Aphanocapsa...

Chlorophyll-binding proteins from the cyanobacterium Aphanocapsa 6714 were identified by immunoblotting procedures. Three chlorophyll-binding complexes, CPIII', CPIIIa, and CPIIIb, were associated with PSII. CPIII' likely serves as an' antenna to PSII in Aphanocapsa since it could be removed from active PSII core preparations without loss of activity. The CPIII' proteins cross-reacted to antibodies prepared against the maize PSII light-harvesting complex, LHC-II. The CPIIIa polypeptides cross-reacted to antibodies raised against the Chlamydomonas PSII chlorophyll-proteins 5 and 6, indicating that this complex contains the major chlorophyll-binding species of the cyanobacterial PSII core. Lastly, an antibody prepared against the canobacterial 36-kDa chlorophyll-binding protein [Pakrasi, H., Riethman, H., and Sherman, L. (1985). Proc. Natl. Acad. Sci. USA 82, 6903-6907] recognized only the 36-kDa IIIb apoprotein, indicating that CPIIIb represents a distinct chlorophyll-protein complex.