Elastic distortion of myosin heads and repriming of the working stroke in muscle

Article Abstract:

X-ray observation of myosin's globular head domain during muscle contraction reveals that the theory that force recovery speed is linked to working stroke reversal is incorrect. Comparisons of alternative stretching and shortening steps through quick muscular stretches of 5 nm per half sarcomere shows that the slow recovery is more likely linked to the release of the interactions between the head domain and the actin filaments. This repriming involves the detachment and the return to the isometric conformation necessary to execute another force-generating working stroke.

Physiological aspects, Observations, Muscle contraction

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Elastic bending and active tilting of myosin heads during muscle contraction

Article Abstract:

Changing the shape of the myosin head region that links myosin and actin filaments drives muscle contraction. Tilting the head's light-chain domain is believed to be linked to ATPase cycle. A new study uses X-ray diffraction and other data from isolated muscle fibers to analyse a head bending that is independent of ATP. The tilting and bending motions together explain force generation in isometric muscle. An atomic model for changes in head configuration is presented.

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The myosin motor in muscle generates a smaller and slower working stroke at higher load

Article Abstract:

A new X-ray-interference technique used to measure the working stroke of myosin II at a constant load, showed that the stroke is smaller and slower at higher loads. Thus the results proved that and efficiency of skeletal muscle was determined by the load dependence of the myosin II stroke.

Science & research, Mechanical movements, Movements (Mechanisms), Skeletal muscle, Intermittent-motion mechanisms

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