Microtubule nanospool formation by active self-assembly is not initiated by thermal activation

Abstract

Biotinylated microtubules partially coated with streptavidin and gliding on a surface coated with kinesin motors can cross-link with each other and assemble into nanospools with a diameter of a few micrometres. The size distribution of these nanospools is determined, and it is shown with simulations of microtubule gliding that these spools are too small to be formed by thermally activated turns in the gliding direction (a Brownian ratchet mechanism). Instead, spool formation is primarily the result of two processes: pinning of gliding microtubules to inactive motors and simultaneous cross-linking of multiple microtubules.