Optimal rectification without forward-current suppression by biological molecular motor.

We experimentally showed that biological molecular motor F$_1$ implements a rectification mechanism that inhibits unfavorable hydrolysis of adenosine triphosphate (ATP) while hardly suppressing ATP synthesis, which is the F$_1$'s physiological role. This optimal rectification is a high contrast to a simple ratchet model, where the inhibition of the backward current is inevitably accompanied by the suppression of the forward current. The detailed analysis of single-molecule trajectories demonstrated a novel but simple rectification mechanism of F$_1$ with parallel landscapes and asymmetric transition rates. Thus, F$_1$ provides a highly optimized function to the cellular energetics by realizing not only the high thermodynamic efficiency but also the suppression of futile ATP consumption.