Stochastic force generation by small ensembles of myosin II motors.
Forces in the actin cytoskeleton are generated by small groups of nonprocessive myosin II motors for which stochastic effects are highly relevant. Using a cross-bridge model with the assumptions of fast power-stroke kinetics and equal load sharing between equivalent states, we derive a one-step master equation for the activity of a finite-sized ensemble of mechanically coupled myosin II motors. For constant external load, this approach yields analytical results for duty ratio and force-velocity relation as a function of ensemble size. We find that stochastic effects cannot be neglected for ensemble sizes below 15. The one-step master equation can be used also for efficient computer simulations with linear elastic external load and reveals the sequence of buildup of force and ensemble rupture that is characteristic for reconstituted actomyosin contractility.
BioQuant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany.
SourcePhysical review letters 108:18 2012 May 4 pg 188101
Myosin Type II
Pub Type(s)Journal Article
Research Support, Non-U.S. Gov't