Rotation scheme of V1-motor is different from that of F1-motor

V-1, a water-soluble portion of vacuole-type ATPase (V-ATPase), is an ATP-driven rotary motor, similar to F-1-ATPase. Hydrolysis of ATP is coupled to unidirectional rotation of the central rotor D and F subunits relative to the A(3)B(3) cylinder. In this study, we analyzed the rotation kinetics of V-1 in detail. At low ATP concentrations, the D subunit rotated stepwise, pausing every 120 degrees. The dwell time between steps revealed that V-1 consumes one ATP per 120 degrees step. V-1 generated torque of approximate to 35 pN nm, slightly lower than the approximate to 46 pN nm measured for F-1. Noticeably, the angles for both ATP cleavage and binding were apparently the same in V-1, in sharp contrast to F-1, which cleaves ATP at 80 degrees posterior to the binding of ATP. Thus, the mechanochemical cycle of V-1 has marked differences to that of F-1.