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 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.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000201:enzymology; D002413:Cations, Divalent; D002417:Cattle; D007700:Kinetics; D008970:Molecular Weight; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D043263:Myosin-Light-Chain Phosphatase; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification* / Q000378:metabolism; D013379:Substrate Specificity
D002413:Cations, Divalent; D000255:Adenosine Triphosphate; D010749:Phosphoprotein Phosphatases; D043263:Myosin-Light-Chain Phosphatase