Non-equilibrium self-assembly of a filament coupled to ATP/GTP hydrolysis

TL;DR

This paper models the stochastic growth and shrinkage of actin filaments and microtubules, incorporating ATP/GTP hydrolysis, revealing distinct dynamic phases and instability features with exact analytical results supported by simulations.

Contribution

It introduces a comprehensive stochastic model of filament dynamics that includes hydrolysis effects and characterizes phase behavior and instability features with exact solutions.

Findings

Identifies three phases: rapid growth, intermediate, and bound.

Provides exact expressions for cap disappearance and collapse times.

Shows hydrolysis influences force-velocity relationships.

Abstract

We study the stochastic dynamics of growth and shrinkage of single actin filaments or microtubules taking into account insertion, removal, and ATP/GTP hydrolysis of subunits. The resulting phase diagram contains three different phases: a rapidly growing phase, an intermediate phase and a bound phase. We analyze all these phases, with an emphasis on the bound phase. We also discuss how hydrolysis affects force-velocity curves. The bound phase shows features of dynamic instability, which we characterize in terms of the time needed for the ATP/GTP cap to disappear as well as the time needed for the filament to reach a length of zero, i.e., (to collapse) for the first time. We obtain exact expressions for all these quantities, which we test using Monte Carlo simulations.