Light chain phosphorylation regulates the movement of smooth muscle myosin on actin filaments

James R. Sellers, James A. Spudich, Michael Sheetz

Research output: Contribution to journalArticle

78 Citations (Scopus)

Abstract

In smooth muscles there is no organized sarcomere structure wherein the relative movement of myosin filaments and actin filaments has been documented during contraction. Using the recently developed in vitro assay for myosin-coated bead movement (Sheetz, M.P., and J.A. Spudich, 1983, Nature (Lond.)., 303: 31-35), we were able to quantitate the rate of movement of both phosphorylated and unphosphorylated smooth muscle myosin on ordered actin filaments derived from the giant alga, Nitella. We found that movement of turkey gizzard smooth muscle myosin on actin filaments depended upon the phosphorylation of the 20-kD myosin light chains. About 95% of the beads coated with phosphorylated myosin moved at velocities beween 0.15 and 0.4 µm/s, depending upon the preparation. With unphosphorylated myosin, only 3% of the beads moved and then at a velocity of only ~0.01-0.04 µm/s. The effects of phosphorylation were fully reversible after dephosphorylation with a phosphatase prepared from smooth muscle. Analysis of the velocity of movement as a function of phosphorylation level indicated that phosphorylation of both heads of a myosin molecule was required for movement and that unphosphorylated myosin appears to decrease the rate of movement of phosphorylated myosin. Mixing of phosphorylated smooth muscle myosin with skeletal muscle myosin which moves at 2 µm/s resulted in a decreased rate of bead movement, suggesting that the more slowly cycling smooth muscle myosin is primarily determining the velocity of movement in such mixtures.

Original languageEnglish (US)
Pages (from-to)1897-1902
Number of pages6
JournalJournal of Cell Biology
Volume101
Issue number5
DOIs
StatePublished - Nov 1 1985
Externally publishedYes

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Smooth Muscle Myosins
Myosins
Actin Cytoskeleton
Phosphorylation
Light
Smooth Muscle
Nitella
Skeletal Muscle Myosins
Myosin Light Chains
Sarcomeres
Phosphoric Monoester Hydrolases

ASJC Scopus subject areas

  • Cell Biology

Cite this

Light chain phosphorylation regulates the movement of smooth muscle myosin on actin filaments. / Sellers, James R.; Spudich, James A.; Sheetz, Michael.

In: Journal of Cell Biology, Vol. 101, No. 5, 01.11.1985, p. 1897-1902.

Research output: Contribution to journalArticle

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