Purification of a myosin phosphatase from bovine aortic smooth muscle

A myosin phosphatase has been purified to homogeneity from bovine aortic smooth muscle. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the enzyme eluted from nondenaturing gels revealed two subunits (Mr = 67,000 and 38,000). Densitometric scans of the subunits indicated a molar ratio o...

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Bibliographic Details
Published in:The Journal of biological chemistry 1982-07, Vol.257 (13), p.7306-7309
Main Authors: Werth, D K, Haeberle, J R, Hathaway, D R
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - pharmacology
Animals
aorta
Aorta - enzymology
Cations, Divalent
Cattle
Kinetics
Molecular Weight
Muscle, Smooth, Vascular - enzymology
Myosin-Light-Chain Phosphatase
phosphoprotein phosphatase
Phosphoprotein Phosphatases - isolation & purification
Phosphoprotein Phosphatases - metabolism
purification
smooth muscle
Substrate Specificity
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Summary:A myosin phosphatase has been purified to homogeneity from bovine aortic smooth muscle. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the enzyme eluted from nondenaturing gels revealed two subunits (Mr = 67,000 and 38,000). Densitometric scans of the subunits indicated a molar ratio of 1:1. Several phosphoproteins were substrates for the phosphatase including histone II-A, isolated 20,000-dalton smooth muscle myosin light chains, phosphorylase a, and smooth muscle myosin. In the presence of 0.25 M NaCl and a substrate concentration of 2 microM, myosin was preferentially dephosphorylated. The specific activity of the phosphatase for myosin at a concentration of 10 microM was found to be 5 mumol/mg/min. The phosphatase required Mn2+ or Co2+ ions for activity. Mg2+, Ca2+, or Mg-ATP would not substitute for Mn2+ or Co2+ at equimolar concentrations. This phosphatase may play an important role in regulating actin-myosin interaction in smooth muscle by serving to dephosphorylate myosin.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(18)34376-X