Single molecule thermodynamics of ATP synthesis by F$_1$-ATPase

TL;DR

This study quantifies the mechanical work and efficiency of the F$_1$-ATPase motor during ATP synthesis at the single-molecule level, revealing minimal internal dissipation even under non-equilibrium conditions.

Contribution

It introduces a novel methodology combining nonequilibrium theory with single-molecule measurements to analyze ATP synthesis by F$_1$-ATPase.

Findings

F$_1$-ATPase efficiently converts mechanical work into chemical energy.

Internal dissipation of the motor is negligible even during rapid rotations.

The motor operates close to thermodynamic efficiency during ATP synthesis.

Abstract

F$_\mathrm{o}$F$_1$-ATP synthase is a factory for synthesizing ATP in virtually all cells. Its core machinery is the subcomplex F$_1$-motor (F$_1$-ATPase) and performs the reversible mechanochemical coupling. Isolated F$_1$-motor hydrolyzes ATP, which is accompanied by unidirectional rotation of its central $\gamma$-shaft. When a strong opposing torque is imposed, the $\gamma$-shaft rotates in the opposite direction and drives the F$_1$-motor to synthesize ATP. This mechanical-to-chemical free-energy transduction is the final and central step of the multistep cellular ATP-synthetic pathway. Here, we determined the amount of mechanical work exploited by the F$_1$-motor to synthesize an ATP molecule during forced rotations using methodology combining a nonequilibrium theory and single molecule measurements of responses to external torque. We found that the internal dissipation of the motor is negligible even during rotations far from a quasistatic process.