Rotation scheme of V1-motor is different from that of F 1-motor

Abstract

V1, a water-soluble portion of vacuole-type ATPase (V-ATPase), is an ATP-driven rotary motor, similar to F1-ATPase. Hydrolysis of ATP is coupled to unidirectional rotation of the central rotor D and F subunits relative to the A3B3 cylinder. In this study, we analyzed the rotation kinetics of V1 in detail. At low ATP concentrations, the D subunit rotated stepwise, pausing every 120°. The dwell time between steps revealed that V1 consumes one ATP per 120° step. V 1 generated torque of ≈35 pN nm, slightly lower than the ≈46 pN nm measured for F1. Noticeably, the angles for both ATP cleavage and binding were apparently the same in V1, in sharp contrast to F 1, which cleaves ATP at 80° posterior to the binding of ATP. Thus, the mechanochemical cycle of V1 has marked differences to that of F1. © 2005 by The National Academy of Sciences of the USA.