Reversal of the Myosin Power Stroke Induced by Fast Stretching of Intact Skeletal Muscle Fibers

AUTOR(ES)

Colombini, Barbara

FONTE

The Biophysical Society

RESUMO

Force generation and movement in skeletal muscle result from a cyclical interaction of overlapping myosin and actin filaments that permits the free energy of ATP hydrolysis to be converted into mechanical work. The rapid force recovery that occurs after a step release imposed on a muscle is thought to result from a synchronized tilting of myosin lever arms toward a position of lower free energy (the power stroke). We investigated the power stroke mechanism in intact muscle fibers of Rana esculenta using a fast stretch to detach forcibly cross-bridges. Stretches were applied either with or without a conditioning step release. Cross-bridge rupture tension was not significantly influenced by the release, whereas sarcomere elongation at the rupture point increased immediately after the release and returned to the prerelease condition within 15–20 ms, following a slower time course compared to the recovery of tension. These observations suggest that the rupture force of a bridge is unaltered by a conditioning release, but rupture must first be preceded by a power stroke reversal, which restores the prepower stroke state. The sarcomere extension at the rupture point indicates both the extent of this power stroke reversal and the time course of strained bridge replenishment.

Documentos Relacionados

• Adult fast myosin pattern and Ca2+-induced slow myosin pattern in primary skeletal muscle culture
• On the regeneration of the actin-myosin power stroke in contracting muscle.
• Novel epigenetic regulation of skeletal muscle myosin heavy chain genes. Focus on “Differential epigenetic modifications of histones at the myosin heavy chain genes in fast and slow skeletal muscle fibers and in response to muscle unloading”
• Differential epigenetic modifications of histones at the myosin heavy chain genes in fast and slow skeletal muscle fibers and in response to muscle unloading
• Expression of aquaporin-4 in fast-twitch fibers of mammalian skeletal muscle.