Berlin 2008 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 12: Cellular Force Generation

BP 12.4: Vortrag

Dienstag, 26. Februar 2008, 18:15–18:30, C 243

Stochastic force generation by small ensembles of myosin II molecular motors — Thorsten Erdmann¹ and •Ulrich Schwarz² — ¹Amolf, Biochemical Networks Group, 1098 SJ Amsterdam, The Netherlands — ²University of Heidelberg, Bioquant 0013, INF 267, 69120 Heidelberg, Germany

Myosin II molecular motors are non-processive and therefore have to work together in ensembles in order to generate appreciable levels of force. In contrast to the situation in muscle, in the actin cytoskeleton (including the actin cortex and stress fibers) myosin II molecular motors usually work in small groups and therefore stochastic effects are expected to be more pronounced. Taking advantage of the separation of time scales present in the myosin II hydrolysis cycle, we are able to reduce the complex network of stochastic transitions within a finite-sized ensemble of myosin II motors to a one-step master equation. We derive analytical expressions for the average time of attachement and the average walk length. We also derive force-velocity relations as a function of ensemble size and compare the average results with exact stochastic simulations of single realizations. Our results show that stochastic effects persist up to a system size of about 15 motors.