Lipids in oxygen-evolving photosystem II complexes of cyanobacteria and higher plants

Lipids in dimeric photosystem II complexes prepared from two species of cyanobacteria, Thermosynechococcus vulcanus and Synechocystis sp. PCC6803, and two higher plants, spinach and rice, were analyzed to determine how many lipid molecules and what class of lipids are present in the photosystem Il complexes. It was estimated that 27, 20, 8, and 7 lipid molecules per monomer are bound to the dimeric photosystem Il complexes of T. vulcanus, Synechocystis, spinach, and rice, respectively. In each of the organisms, the lipid composition of the photosystem 11 complexes was quite different from that of the thylakoid membranes used for preparation of the complexes. The content of phosphatidylglycerol. in the photosystem 11 complexes of each organism was much higher than that in the thylakoid membranes. Phospholipase A(2) treatment of the photosystem 11 complexes of Synechocystis that degraded phosphatidylglycerol resulted in impairment of Q(B)-mediated but not Q(A)-mediated electron transport. These findings suggest that phosphatidylglycerol plays important roles in the electron transport at the Q(B)-binding site in photosystem 11 complexes.