Pulling cargo increases the precision of molecular motor progress

TL;DR

This paper demonstrates that explicitly modeling cargo diffusion reveals increased precision in molecular motor progress, challenging previous assumptions based on constant-force approximations and providing new bounds on motor accuracy.

Contribution

It introduces a more accurate model of cargo influence on molecular motors, showing increased precision and proposing a new bound independent of motor cycle stages.

Findings

Explicit cargo diffusion modeling increases motor progress precision.

Constant-force approximation overestimates variance in motor steps.

Low diffusivity cargo leads to a new bound on motor precision.

Abstract

Biomolecular motors use free energy to drive a variety of cellular tasks, including the transport of cargo, such as vesicles and organelles. We find that the widely-used `constant-force' approximation for the effect of cargo on motor dynamics leads to a much larger variance of motor step number compared to explicitly modeling diffusive cargo, suggesting the constant-force approximation may be misapplied in some cases. We also find that, with cargo, motor progress is significantly more precise than suggested by a recent result. For cargo with a low relative diffusivity, the dynamics of continuous cargo motion---rather than discrete motor steps---dominate, leading to a new, more permissive bound on the precision of motor progress which is independent of the number of stages per motor cycle.