Phosphorylation kinetics of skeletal muscle myosin and the effect of phosphorylation on actomyosin adenosinetriphosphatase activity

Anthony Persechini, James T. Stull

Research output: Contribution to journalArticle

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Abstract

Purified rabbit skeletal muscle myosin is phosphorylated on one type of light-chain subunit (P-light chain) by calmodulin-dependent myosin light chain kinase and dephosphorylated by phosphoprotein phosphatase C. Analyses of the time courses of both phosphorylation and dephosphorylation of skeletal muscle myosin indicated that both reactions, involving at least 90% of the P-light chain, were kinetically homogeneous. These results suggest that phosphorylation and dephosphorylation of rabbit skeletal muscle myosin heads are simple random processes in contrast to the sequential phosphorylation mechanism proposed for myosin from gizzard smooth muscle. We also examined the effect of phosphorylation of rabbit skeletal muscle myosin on the actin-activated ATPase activity. We observed an apparent 2-fold decrease in the Km for actin, from about 6 μM to about 2.5 μM, with no significant effect on the Vmax (1.8 s-1) in response to P-light-chain phosphorylation. There was no significant effect of phosphorylation on the ATPase activity of myosin alone (0.045 s-1). ATPase activation could be fully reversed by addition of phosphatase catalytic subunit. The relationship between the extents of P-light-chain phosphorylation and ATPase activation (at 3.5 μM actin and 0.6 μM myosin) was essentially linear. Thus, in contrast to results obtained with myosin from gizzard smooth muscle, these results suggest that cooperative interactions between the myosin heads do not play an important role in the activation process in skeletal muscle. Since the effect of P-light-chain phosphorylation is upon the Km for actin, it would appear to be associated with a significant activation of ATPase activity only at appropriate concentrations of actin and salt. Myosin preparations stored for longer than 5 days at 0°C have been found to have no significant response to P-light-chain phosphorylation, and the effect of aging was an enhancement of ATPase activity in the absence of phosphorylation.

Original languageEnglish (US)
Pages (from-to)4144-4150
Number of pages7
JournalBiochemistry
Volume23
Issue number18
StatePublished - 1984

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Skeletal Muscle Myosins
Phosphorylation
Myosins
Kinetics
Light
Adenosine Triphosphatases
Actins
Chemical activation
Smooth Muscle Myosins
Muscle
Rabbits
Myosin-Light-Chain Kinase
Phosphoprotein Phosphatases
Calmodulin
Random processes
Phosphoric Monoester Hydrolases
Catalytic Domain
Skeletal Muscle
Salts
Aging of materials

ASJC Scopus subject areas

  • Biochemistry

Cite this

Phosphorylation kinetics of skeletal muscle myosin and the effect of phosphorylation on actomyosin adenosinetriphosphatase activity. / Persechini, Anthony; Stull, James T.

In: Biochemistry, Vol. 23, No. 18, 1984, p. 4144-4150.

Research output: Contribution to journalArticle

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