Conformation of the myosin motor during force generation in skeletal muscle |
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Authors: | Irving M Piazzesi G Lucii L Sun Y B Harford J J Dobbie I M Ferenczi M A Reconditi M Lombardi V |
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Affiliation: | School of Biomedical Sciences, King's College London, London, UK. malcolm.irving@kcl.ac.uk |
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Abstract: | Myosin motors drive muscle contraction, cytokinesis and cell locomotion, and members of the myosin superfamily have been implicated in an increasingly diverse range of cell functions. Myosin can displace a bound actin filament several nanometers in a single interaction. Crystallographic studies suggest that this 'working stroke' involves bending of the myosin head between its light chain and catalytic domains. Here we used X-ray fiber diffraction to test the crystallographic model and measure the interdomain bending during force generation in an intact single muscle fiber. The observed bending has two components: an elastic distortion and an active rotation that generates force. The average bend of the force-generating myosin heads in a muscle fiber is intermediate between those in crystal structures with different bound nucleotides, and the C-terminus of the head is displaced by 7 nm along the actin filament axis compared with the in vitro conformation seen in the absence of nucleotide. |
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