Dresden 2017 – scientific programme

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BP: Fachverband Biologische Physik

BP 43: Cytoskeletal Filaments

BP 43.3: Talk

Wednesday, March 22, 2017, 15:45–16:00, HÜL 386

Electron Microscopy (EM) and Single Particle Analysis on Myosin — •Dario Saczko-Brack, Christopher Batters, Benoit Rogez, Markus Kröss, and Claudia Veigel — LMU, Department of Cellular Physiology, Schillerstrasse 44, 80336 Munich, Germany

Myosin-IX is critically involved in structural reorganizations of the acto-myosin cytoskeleton in the lamellipodium of migrating cells and in cell polarization in morphogenesis. Using a combination of negative stain EM, single particle image processing, fluorescence spectroscopy and motility assays we discovered that myosin-IXa assembles actin filaments into highly ordered lattices with parallel actin polarity and a repeat distance of precisely 36 nm, matching the helical repeat of actin. We resolved three distinct conformations of myosin-IXa crosslinks in the absence of nucleotide. Furthermore we found that calmodulin binds to a large insert in the motor domain exclusively found in class IX myosins. This creates two coordinated actin binding sites that constrain the acto-myosin interactions which generates the lattices. These might introduce a myosin-related, force-sensing mechanism into the cytoskeleton in cell polarization and collective cell migration.

The cytoskeletal motor myosin VI is involved in many motile processes including cancer cell migration and is the only myosin shown to move towards the minus end of actin. We demonstrate that calcium is the cellular switch that induces a structural rearrangement of this motor which regulates the transition from an inactive to a cargo-binding state and controls the mechanical properties.

Batters, Brack et al. PNAS 2016