Electrical stimulation of isolated mouse fast-twitch muscles revealed that activation involves disruption of the helical array of myosin motors, release from the folded conformation, and actin attachment.
This study reveals the structural basis for myosin-based regulation of twitch and tetanic contractions in mammalian skeletal muscle, including the mechanism of post-tetanic potentiation.
Time-resolved X-ray diffraction of isolated fast-twitch muscles of mice was used to show how structural changes in the myosin-containing thick filaments contribute to the regulation of muscle contraction, extending the previous focus on regulation by the actin-containing thin filaments. This study shows that muscle activation involves the following sequence of structural changes: thin filament activation, disruption of the helical array of myosin motors characteristic of resting muscle, release of myosin motor domains from the folded conformation on the filament backbone, and actin attachment. Physiological force generation in the 'twitch' response of skeletal muscle to single action potential stimulation is limited by incomplete activation of the thick filament and the rapid inactivation of both filaments. Muscle relaxation after repetitive stimulation is accompanied by a complete recovery of the folded motor conformation on the filament backbone but by incomplete reformation of the helical array, revealing a structural basis for post-tetanic potentiation in isolated muscles.
Hill et al. (Mon,) reported a other. Electrical stimulation (twitch and tetanic contractions) vs. Resting state was evaluated on Structural changes in myosin-containing thick filaments measured by X-ray diffraction. Electrical stimulation of isolated mouse fast-twitch muscles revealed that activation involves disruption of the helical array of myosin motors, release from the folded conformation, and actin attachment.
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