Condensation of actin filaments pushing against a barrier

TL;DR

This paper models how parallel actin filaments generate force against a barrier, revealing a transition from a spread-out to a condensed filament arrangement at high force, and confirming the stall force relation.

Contribution

It introduces a combined mean-field and simulation approach to analyze filament density and force-velocity relations, identifying a condensed regime and confirming the stall force scaling.

Findings

Identifies two regimes: non-condensed and condensed filaments.

Confirms stall force equals N times single filament stall force.

Shows slow approach to stalling at high forces.

Abstract

We develop a model to describe the force generated by the polymerization of an array of parallel biofilaments. The filaments are assumed to be coupled only through mechanical contact with a movable barrier. We calculate the filament density distribution and the force-velocity relation with a mean-field approach combined with simulations. We identify two regimes: a non-condensed regime at low force in which filaments are spread out spatially, and a condensed regime at high force in which filaments accumulate near the barrier. We confirm a result previously known from other related studies, namely that the stall force is equal to N times the stall force of a single filament. In the model studied here, the approach to stalling is very slow, and the velocity is practically zero at forces significantly lower than the stall force.