Dresden 2014 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 1: Molecular Motors
BP 1.8: Vortrag
Montag, 31. März 2014, 11:45–12:00, HÜL 386
Dynamical Phenomena in Coupled Muscle Myosins — •Lennart Hilbert, Zsombor Balassy, Shivaram Cumarasamy, Anne-Marie Lauzon, and Michael C. Mackey — McGill University, Montréal, Québec, Canada
The length (l) of muscle myosin filaments in smooth muscle cells is distributed following exp(−l/L0), L0=0.116− 0.182 µ m [Liu et al., J Physiol, 2013]. The kinetics of skeletal muscle myosin groups working on a commonly propelled actin filament qualitatively change at L1c≈ 0.3 µ m and L2c≈ 1.0 µ m lengths of interaction between a myosin-coated surface and myosin-propelled actin filaments (L, motility assay) [Hilbert et al., Biophys J, 2013]. In this study, motility assays of smooth muscle myosin showed the same kinetic regimes for increasing L as seen for skeletal muscle myosin: (1) actin arrest to surface, (2) alternating arrest and forward sliding (autocorrelation time 0.3 s), (3) continuous forward sliding; transition lengths L1c ≈ 0.27 µ m and L2c≈ 0.75 µ m. The regimes were reproduced by a mathematical model of N=5 to 100 myosin binding sites (N∝ L) on individual actin filaments interacting with surface-fixed myosins. Binding site kinetics were mechanically coupled via actin, and dependent on L, a stable focus (arrest) and a limit cycle (sliding) existed that entrained global behavior. The dynamic phenomena and resulting L-dependent statistics from our actin sliding experiments were captured by a reduced mathematical model with two fast variables (exhibiting limit cycle or stable focus) and one slow variable (switching between cycle and focus).