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Myosin Filament Structure - Invertebrates

Myosin filaments (also called thick filaments) are polymers of myosin II. For decades there was little understanding of how filaments were constructed nor how myosin motors functioned. We have used conventional cryo-EM to preserve native filament structure, and single particle techniques to carry out 3D reconstruction of myosin filaments from tarantula (a model system for filament structure). Our results show that the two heads of myosin interact with each other in relaxed muscle. These interactions block sites needed for actin interaction and ATP hydrolysis, which switches thick filament  activity off. We have recently shown that the IHM is common to every type of thick filament so far studied. It arose early in evolution and is fundamental to muscle function. Our question now is: what are the atomic-level interactions that underlie this inhibition of activity? We are using the state-of-the-art cryo-EM instrumentation at the medical school to obtain atomic detail.

Roger Craig Lab - UMass Medical School - Taran fitting