Structure and dynamics of motor-driven microtubule bundles

TL;DR

This study investigates how polyethylene glycol influences the internal structure and dynamics of microtubule-kinesin bundles, revealing a transition from sliding to extension correlated with structural rearrangements, advancing understanding of active material behaviors.

Contribution

It demonstrates how crowding agents alter microtubule bundle structures and dynamics, linking microscopic rearrangements to macroscopic extensile behavior in active materials.

Findings

Increased polyethylene glycol concentration causes a transition from sliding to pure extension.

Microtubule bundles change from open hexagonal to compressed rectangular lattice.

Bundles exhibit similar extensile behaviors despite internal structural differences.

Abstract

Connecting the large-scale emergent behaviors of active materials to the microscopic properties of their constituents is a challenge due to a lack of data on the multiscale dynamics and structure of such systems. We approach this problem by studying the impact of polyethylene glycol, a crowding agent, on bundles of microtubules and kinesin-14 molecular motors. Bundles assembled in the presence of either low or high concentrations of polyethylene glycol generate similar net extensile behaviors. However, as polyethylene glycol concentration is increased, the motion of microtubules in the bundles transition from bi-directional sliding with extension to pure extension with no sliding. Small-angle X-ray scattering shows that the transition in microtubule dynamics is concomitant with a rearrangement of microtubules in the bundles from an open hexagonal to a compressed rectangular lattice. These results demonstrate that bundles of microtubules and molecular motors can display similar mesoscopic extensile behaviors despite having very different internal structures and dynamics.