Phosphorylation of smooth muscle myosin light chains by cAMP-dependent protein kinase.
The 20,000-dalton light chain of chicken gizzard myosin was phosphorylated in vitro by the cAMP-dependent protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) from bovine heart. The enzyme catalyzed incorporation of 1 mol of Pi/mol of light chain in a reaction that was completely dependent upon cAMP and independent of Ca2+. Two-dimensional peptide mapping of alpha-chymotryptic digests, as well as phosphoamino acid analysis of acid hydrolysates, were used to compare the site phosphorylated by cAMP-dependent protein kinase to that phosphorylated by turkey gizzard myosin light chain kinase. The results indicate that both enzymes phosphorylate the same serine residue. However, the light chains were a better in vitro substrate for myosin light chain kinase than for cAMP-dependent protein kinase. The amino acid sequence around the phosphorylated serine is characteristic of substrates of cAMP-dependent protein kinases.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D002645:Chickens; D000242:Cyclic AMP / Q000494:pharmacology; D005895:Gizzard, Avian / Q000378:metabolism; D007700:Kinetics; D009130:Muscle, Smooth / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D010748:Phosphopeptides / Q000032:analysis; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*
D000596:Amino Acids; D010446:Peptide Fragments; D010748:Phosphopeptides; D000242:Cyclic AMP; D011494:Protein Kinases; D009218:Myosins