Cooperative molecular motors moving back and forth

TL;DR

This study models the cooperative bidirectional movement of molecular motors on cytoskeletal tracks with alternating polarities, revealing how elastic tension influences reversal times and directionality.

Contribution

It introduces a two-state ratchet model incorporating elastic tension effects, showing their impact on motor cooperation and bidirectional motion dynamics.

Findings

Elastic tension reduces reversal times in motor systems.

Bidirectional motion occurs mainly on a-polar tracks.

Motion becomes unidirectional on slightly polar tracks.

Abstract

We use a two-state ratchet model to study the cooperative bidirectional motion of molecular motors on cytoskeletal tracks with randomly alternating polarities. Our model is based on a previously proposed model [Badoual et al., {\em Proc. Natl. Acad. Sci. USA} {\bf 99}, 6696 (2002)] for collective motor dynamics and, in addition, takes into account the cooperativity effect arising from the elastic tension that develops in the cytoskeletal track due to the joint action of the walking motors. We show, both computationally and analytically, that this additional cooperativity effect leads to a dramatic reduction in the characteristic reversal time of the bidirectional motion, especially in systems with a large number of motors. We also find that bidirectional motion takes place only on (almost) a-polar tracks, while on even slightly polar tracks the motion is unidirectional. We argue that the origin of these observations is the sensitive dependence of the cooperative dynamics on the difference between the number of motors typically working in and against the instantaneous direction of motion.