Electric Field Driven Torque in ATP Synthase

TL;DR

This paper proposes a novel electric field mechanism driving the rotation of ATP synthase's c-ring, linking proton motive force to torque generation and ATP production rates, with implications for understanding energy conversion in cells.

Contribution

It introduces a new model where electric fields from proton channels induce torque in ATP synthase, explaining how proton motive force drives rotation and ATP synthesis.

Findings

Torque scales with proton motive force.

Mutations affecting channels hinder torque.

ATP production rate depends on proton binding sites.

Abstract

Fo-ATP synthase (Fo) is a rotary motor that converts potential energy from ions, usually protons, moving from high- to low-potential sides of a membrane into torque and rotary motion. Here we propose a mechanism whereby electric fields emanating from the proton entry and exit channels act on asymmetric charge distributions in the c-ring, due to protonated and deprotonated sites, and drive it to rotate. The model predicts a scaling between time-averaged torque and proton motive force, which can be hindered by mutations that adversely affect the channels. The torque created by the c-ring of Fo drives the gamma-subunit to rotate within the ATP-producing complex (F1) overcoming, with the aid of thermal fluctuations, an opposing torque that rises and falls with angular position. Using the analogy with thermal Brownian motion of a particle in a tilted washboard potential, we compute ATP production rates vs. proton motive force. The latter shows a minimum, needed to drive ATP production, which scales inversely with the number of proton binding sites on the c-ring.