Fig. 7. The rotary mechanism of V/A-ATPase powered by ATP hydrolysis.
The schematic models of ABopen, ABsemi, and ABclosed are shown in green, pink, and blue, respectively. The coiled-coil region of the D subunit in contact with A3B3 is shown in gray. In the ADP inhibited state, the entrapped ADP in ABclosed hampers the structural transition of ABopen to ABsemi by binding of ATP to ABopen. The Vnucfree in the ground state is activated by the binding of ATP to the catalytic sites. In V2nuc awaiting ATP binding, binding of ATP to ABopen does not induce the 120° rotation step. In V3nuc, both zipper motion of ABopen and ATP hydrolysis in ABsemi induce unzipper motion of ABclosed accompanying the release of ADP and Pi. The catalytic events in the three AB dimers occur simultaneously with the 120˚ step of the DF shaft, resulting in the structural transition of state1 of V3nuc to state2 of V2nuc.