Inter-filament Attractions Narrow the Length Distribution of Actin Filaments

TL;DR

This study demonstrates that inter-filament attractions caused by crosslinkers, counterions, or depletion forces significantly narrow the length distribution of actin filaments, influencing their average length and alignment.

Contribution

It introduces a simple theoretical model explaining how short-range attractions lead to longer, more aligned actin filaments, a novel insight into filament length regulation.

Findings

Attractions narrow the filament length distribution

Short-range attractions increase average filament length

Filament alignment is promoted by inter-filament attractions

Abstract

We show that the exponential length distribution that is typical of actin filaments under physiological conditions dramatically narrows in the presence of (i) crosslinker proteins (ii) polyvalent counterions or (iii) depletion mediated attractions. A simple theoretical model shows that in equilibrium, short-range attractions enhance the tendency of filaments to align parallel to each other, eventually leading to an increase in the average filament length and a decrease in the relative width of the distribution of filament lengths.