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BP: Fachverband Biologische Physik
BP 49: Molecular motors
BP 49.6: Vortrag
Donnerstag, 19. März 2015, 18:15–18:30, H 1028
Filamin Inhibition of Myosin Groups Potentiates with Group Size — Zsombor Balassy1, •Lennart Hilbert1,2, Nedjma B Zitouni1, and Anne-Marie Lauzon1 — 1McGill University, Montréal, Canada — 2Center for Systems Biology, Dresden, Germany
Filamin is an actin-actin crosslinker found in smooth muscle and non-muscle cells and inhibitis actin filament sliding in in vitro motility assays. Here, we investigate how inhibition by filamin scales with myosin group size. In our in vitro motility assay (smooth muscle myosin), filamin did not disrupt the bistable stop-and-go motion of actin [1], did not affect the velocity of sliding actin, but decreased the fraction of actin in the sliding state (fmot). Full arrest occurred for [Filamin]=15 nM ([Actin] = 30 nM). For [Filamin]=5 nM, fmot had a maximum (fmot=0.6) at intermediate actin length (L=1.0 µ m). For shorter actin, fmot displayed the typical reduction to lower fmot. For longer actin, however, an atypical decrease of fmot with L was observed (fmot=0.45 for L=1.7 µ m). We extended our mathematical model of actin propulsion by myosin groups [1] and reproduced these results. The model now explicitly treats the location of myosin and filamin binding sites on actin (spacing 35.5 nm), mechanical coupling strength decays exponentially along actin (characteristic length 175 nm). In the model, filamin binding is established and resolved in locally confined domains, each of which can lead to global arrest of actin sliding. On longer actin there are more localized domains, each of which can independently arrest the whole filament, leading to a greater likelihood of arrest. [1] Hilbert et al., Biophys J, 2013