Phosphorylation of smooth muscle actin by the catalytic subunit of the cAMP-dependent protein kinase |
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Authors: | M P Walsh S Hinkins D J Hartshorne |
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Institution: | 1. Muscle Biology Group, Department of Biochemistry, College of Agriculture, The University of Arizona, Tucson, AZ 85721 USA;2. Department of Nutrition and Food Science, College of Agriculture, The University of Arizona, Tucson, AZ 85721 USA |
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Abstract: | Partially purified smooth muscle (chicken gizzard) actomyosin contains two major substrates of cAMP-dependent protein kinase: a protein of Mr = 130,000, identified as the calmodulin-dependent myosin light chain kinase, and a protein of Mr = 42,000. This latter protein was shown by a variety of electrophoretic procedures to be actin. Purified smooth muscle actin also was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase. The rate of phosphorylation of smooth muscle actin was significantly enhanced by depolyjerization of actin. A maximum of 2.0 mol phosphate could be incorporated per mol G-actin. Skeletal muscle F-actin was not significantly phosphorylated by protein kinase; however, skeletal G-actin is a substrate for the protein kinase although its rate of phosphorylation was significantly slower than that of smooth muscle G-actin. |
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Keywords: | EGTA MLCK myosin light chain kinase PAGE polyacrylamide gel electrophoresis SDS sodium dodecyl sulfate |
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