Mechanism of torque transmission from F_o to F_1 in ATP synthase

Determine the detailed physical mechanism by which the F_o motor of the F_oF_1-ATP synthase transmits torque to the F_1 γ-shaft to drive ATP synthesis, including the nature of the elastic coupling and the torque-delivery process from F_o to F_1 under experimental and physiological conditions.

Background

F_oF_1-ATP synthase is a bifunctional rotary enzyme where F_o uses the proton motive force to rotate a c-ring, transmitting torque through the connected γ-shaft in F_1, which synthesizes ATP every 120° rotation. While structural details of the holoenzyme are well resolved, how the mechanical coupling transduces torque from F_o to F_1 remains incompletely characterized.

This paper investigates efficient external control of F_1 rotation (constant torque versus angle clamp), showing angle clamp reduces dissipation by suppressing nonequilibrium variation. The unresolved question of the native torque-transmission mechanism is central for interpreting how in vivo driving might achieve high efficiency and how the elastic coupling mediates dynamic control between the two motors.