Design principles and optimal performance for molecular motors under realistic constraints

TL;DR

This paper explores the design principles of molecular motors, revealing how gating mechanisms and interaction tradeoffs influence their power, efficiency, and maximum torque under realistic biological constraints.

Contribution

It introduces a thermodynamic framework and simulations to identify optimal motor design strategies balancing power and efficiency in realistic conditions.

Findings

Gating mechanisms are essential for high power output.

Maximum torque at stall is below theoretical limits due to speed fluctuations.

Tradeoff between interaction strength and back steps limits efficiency.

Abstract

The performance of a molecular motor, characterized by its power output and energy efficiency, is investigated in the motor design space spanned by the stepping rate function and the motor-track interaction potential. Analytic results and simulations show that a gating mechanism that restricts forward stepping in a narrow window in configuration space is needed for generating high power at physiologically relevant loads. By deriving general thermodynamics laws for nonequilibrium motors, we find that the maximum torque (force) at stall is less than its theoretical limit for any realistic motor-track interactions due to speed fluctuations. Our study reveals a tradeoff for the motor- track interaction: while a strong interaction generates a high power output for forward steps, it also leads to a higher probability of wasteful spontaneous back steps. Our analysis and simulations show that this tradeoff sets a fundamental limit to the maximum motor efficiency in the presence of spontaneous back steps, i.e., loose-coupling. Balancing this tradeoff leads to an optimal design of the motor-track interaction for achieving a maximum efficiency close to 1 for realistic motors that are not perfectly coupled with the energy source.Comparison with existing data and suggestions for future experiments are discussed.