TENTOXIN INHIBITS BOTH PHOTOPHOSPHORYLATION IN THYLAKOIDS AND THE ATPASE ACTIVITY OF ISOLATED COUPLING FACTOR-F1 FROM THE CYANOBACTERIUM ANACYSTIS-NIDULANS

Tentoxin strongly inhibited the ATPase activity of isolated coupling factor 1 (AF1) from the cyanobacterium Anacystis nidulans, with 50% inhibition occurring at 0.3 muM. When thylakoids from A. nidulans were preincubated with 0.3 muM tentoxin for 30 min, photophosphorylation was inhibited by 50%. Measurements of fluorescence from 9-aminoacridine indicated that tentoxin inhibited the utilization of the proton gradient by ATP formation in thylakoids. These results indicate that tentoxin is a strong energy-transfer inhibitor of photophosphorylation in A. nidulans. Tentoxin decreased the level of ATP in intact cells both in the light and in darkness, its effects being much stronger in the dark. Tentoxin at 50 muM strongly inhibited the growth of the cells.