The number of functional catalytic sites on F1-ATPases and the effects of quaternary structural asymmetry on their properties.

Recent structural and kinetic studies of F1 and F0F1 are reviewed with regard to their implications for the binding change mechanism for ATP synthesis by oxidative phosphorylation and photophosphorylation. It is concluded that at least two and probably all three of the catalytic sites on F1 are functionally equivalent despite permanent structural asymmetry in the soluble enzyme. A rotary mechanism in which all three catalytic subunits experience all possible interactions with the single-copy subunits during turnover is thought not to apply to soluble F1 but remains an attractive model for the membrane bound enzyme.