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Physiological Significance of Myosin Phosphorylation in Skeletal Muscle

1993; NRC Research Press; Volume: 18; Issue: 3 Linguagem: Inglês

10.1139/h93-020

1543-2718

Robert W. Grange, Rene Vandenboom, Michael E. Houston,

Ion channel regulation and function

Each S-I or head portion of the myosin molecule in skeletal muscle contains a subunit known as the regulatory or phosphorylatable light chain (P-LC). Phosphorylation of the P-LC is mediated by the second messenger Ca 2+ and takes place when the muscle fibre is activated. In smooth muscle, phosphorylation of the P-LC is the principal mechanism that initiates contraction, but in skeletal muscle myosin P-LC phosphorylation is not required for contraction and a definitive role has not been established. It has been proposed that P-LC phosphorylation modulates the intrinsic nature of actin-myosin interactions, leading to force potentiation under suboptimal activation conditions. An example of this is posttetanic potentiation. This paper describes a P-LC phosphorylation induced mechanism for force enhancement during isometric contraction. In addition, it summarizes recent data revealing that P-LC phosphorylation is associated with enhanced work output of fast-twitch muscle during shortening and lengthening contractions. Key words: contractile properties, mouse muscle, human muscle, work, power