In recent bibliography I consulted for a research related with cyanobacteria, I found a paper where they talk about the inhibitory effects on ATP synthase of Microcystins: A. Mikhailov, A.S. Harmala-Brasken, J. Hellman, J. Meriluoto, J.E. Eriksson Identification of ATP synthase as a novel intracellular target for microcystin-LR Chem. Biol. Interact, 142 (2003), pp. 223–237