The myosin catalytic domain does not rotate during the working power stroke.
Electron paramagnetic resonance spectroscopy of a spin probe attached to cys-707 on myosin cross-bridges was used to monitor the orientation of the myosin catalytic domain at the beginning and end of the working power stroke in active muscle. Elevated concentrations of orthophosphate and decreased pH were used to shift the population of cross-bridges from force-producing states into low force, pre-power-stroke states. The spectrum of probes in active fibers was not changed by conditions that reduced tension by 70%, indicating that the orientation of the catalytic domain was the same at the beginning and end of the power stroke. Thus the data show that the catalytic domain remains rigidly oriented on the actin filament during the power stroke.
Department of Biochemistry and Biophysics, University of California, San Francisco 94143, USA.
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Zhao
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Baker
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D000818:Animals; D001665:Binding Sites; D003497:Cyclic N-Oxides; D003545:Cysteine; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009218:Myosins / Q000737:chemistry* / Q000502:physiology*; D010710:Phosphates / Q000494:pharmacology; D011817:Rabbits; D013113:Spin Labels
D003497:Cyclic N-Oxides; D010710:Phosphates; D013113:Spin Labels; C024516:N-(1-oxyl-2,2,5,5-tetramethyl-3-pyrrolidinyl)maleimide; D009218:Myosins; D003545:Cysteine