Cooperative Lattice Dynamics and Anomalous Fluctuations of Microtubules

TL;DR

This paper presents evidence for discrete conformational states and cooperative dynamics in microtubules, proposing a new model that explains their anomalous fluctuations and elastic properties through polymorphic lattice behavior.

Contribution

It introduces a novel microtubule model based on tubulin bistability and cooperativity, explaining previously conflicting experimental observations.

Findings

Microtubules exhibit discrete GDP-tubulin conformational fluctuations.

Microtubules can spontaneously form micron-sized cooperative helical states.

The polymorphic lattice dynamics explain anomalous fluctuation scaling and curvature in microtubules.

Abstract

Microtubules have been in biophysical focus for several decades. Yet the confusing and mutually contradicting results regarding their elasticity and fluctuations have shed some doubts on their present understanding. In this paper we expose the empirical evidence for the existence of discrete GDP-tubulin fluctuations between a curved and a straight configuration at room temperature as well as for conformational tubulin cooperativity. Guided by a number of experimental findings, we build the case for a novel microtubule model, with the principal result that microtubules can spontaneously form micron size cooperative helical states with unique elastic and dynamic features. The polymorphic dynamics of the microtubule lattice resulting from the tubulin bistability quantitatively explains several experimental puzzles including anomalous scaling of dynamic fluctuations of grafted microtubules, their apparent length-stiffness relation and their remarkably curved-helical appearance in general. We point out that tubulin dimers's multistability and its cooperative switching could participate in important cellular processes, and could in particular lead to efficient mechanochemical signalling along single microtubules.