Why Microtubules run in Circles - Mechanical Hysteresis of the Tubulin Lattice

TL;DR

This paper presents a model explaining the formation of arcs and rings in microtubules through a conformational switch in the tubulin lattice, revealing their mechanical hysteresis and polymorphic states.

Contribution

It introduces a novel model of microtubule lattice mechanics based on conformational switching, explaining long-lived arcs and rings observed in experiments.

Findings

Microtubule lattice exhibits discrete polymorphic states.

Mechanical hysteresis can induce curved conformations in microtubules.

Microtubules are highly resistant to breakage under cellular forces.

Abstract

The fate of every eukaryotic cell subtly relies on the exceptional mechanical properties of microtubules. Despite significant efforts, understanding their unusual mechanics remains elusive. One persistent, unresolved mystery is the formation of long-lived arcs and rings, e.g. in kinesin-driven gliding assays. To elucidate their physical origin we develop a model of the inner workings of the microtubule's lattice, based on recent experimental evidence for a conformational switch of the tubulin dimer. We show that the microtubule lattice itself coexists in discrete polymorphic states. Curved states can be induced via a mechanical hysteresis involving torques and forces typical of few molecular motors acting in unison. This lattice switch renders microtubules not only virtually unbreakable under typical cellular forces, but moreover provides them with a tunable response integrating mechanical and chemical stimuli.