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AKB: Biologische Physik

AKB 25: Active Networks and Cell Motility

AKB 25.1: Vortrag

Freitag, 4. März 2005, 15:30–15:45, TU H2013

Molecular motors in cells: A rapid switch of biopolymer organization — •David Smith¹, Falko Ziebert², Walter Zimmermann², and Josef Käs¹ — ¹Institute for Soft Matter Physics, University of Leipzig, Linné Str. 5, D-04103 Leipzig, Germany — ²Theoretical Physics, University of the Saarland, D-66041 Saarbrücken, Germany

All eukaryotic cells rely on the self-assembly of protein filaments to form a cytoskeleton. Motility and reaction to stimuli require pathways to reversibly change cytoskeletal organization. We report a mechanism whereby the molecular motor myosin II induces order-disorder transitions in actin-myosin networks. Bulk activity of the motors, which causes sliding on an individual filament level, maintains a dynamically disordered network. During depletion of ATP, an increasing fraction of molecular motors becomes inactive, crosslinking actin filaments to small clusters. The remaining active motors combined with continually increasing cross-linking foster further growth of these clusters, resulting in a variety of ordered macro-molecular structures such as asters, networks resembling neuronal architectures, and condensed super-precipitates. Experiments with photo-activated motors demonstrate the quick reversible restoration of the disordered state. This nonequilibrium pathway to switch between order and disorder is much faster than any structural changes driven by Brownian motion in thermodynamic equilibrium. This ability for rapid, isothermal motor-induced transitions between different degrees of self-organization indicates that molecular motors, in general, may substantially contribute to dynamic cellular organization.