Phosphorylation of myosin light chain by a protease-activated kinase from rabbit skeletal muscle.
A protease-activated protein kinase that phosphorylates the P light chain of myosin in the absence of Ca2+ and calmodulin has been isolated from rabbit skeletal muscle. The enzyme has properties similar to protease-activated kinase I from rabbit reticulocytes [S. M. Tahara and J. A. Traugh (1981) J. Biol. Chem. 256, 11588-11564], which has been shown to phosphorylate the P light chain of myosin [P. T. Tuazon, J. T. Stull, and J. A. Traugh (1982) Biochem. Biophys. Res. Commun. 108, 910-917]. The protease-activated kinase from skeletal muscle has been partially purified by chromatography on DEAE-cellulose, phosphocellulose and hydroxyapatite. The enzyme phosphorylates histone as well as the P light chain of myosin following activation by proteolysis. Stoichiometric phosphorylation of myosin light chain was observed with the protease-activated kinase and myosin light chain kinase. The sites phosphorylated by the protease-activated kinase and myosin light chain kinase were examined by two-dimensional peptide mapping following chymotryptic digestion. The phosphopeptides observed with the protease-activated kinase were different from those obtained with the Ca2+-dependent myosin light chain kinase, indicating that the two enzymes phosphorylated different sites on the P light chain of skeletal muscle myosin. When actomyosin from skeletal muscle was examined as substrate, the P light chain was phosphorylated following activation of the protease-activated kinase by limited proteolysis.
D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D009132:Muscles / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D010447:Peptide Hydrolases / Q000494:pharmacology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits
D010446:Peptide Fragments; D011494:Protein Kinases; D010447:Peptide Hydrolases; D009218:Myosins