Inhibitory Mg-ADP--Fluoroaluminate Complexes Bound to Catalytic Sites of F1-ATPases: Are They Ground-State or Transition-State Analogs?

Schemes are proposed for coupling sequential opening and closing the three catalytic sites of F^sub 1^ to rotation of the γ subunit during ATP synthesis and hydrolysis catalyzed by the F^sub o^F^sub 1^-ATP synthase. A prominent feature of the proposed mechanisms is that the transition state during ATP synthesis is formed when a catalytic site is in the process of closing and that the transition state during ATP hydrolysis is formed when a catalytic site is in the process of opening. The unusual kinetics of formation of Mg-ADP--fluoroaluminate complexes in one or two catalytic sites of nucleotide-depleted MF^sub 1^ and wild-type and mutant α^sub 3^β^sub 3^γ subcomplexes of TF^sub 1^ are also reviewed. From these considerations, it is concluded that Mg-ADP--fluoroaluminate complexes formed at catalytic sites of isolated F^sub 1^-ATPases or F^sub 1^ in membrane-bound F^sub o^F^sub 1^ are ground-state analogs.[PUBLICATION ABSTRACT]