Noiman E S
J Biol Chem. 1980 Dec 10;255(23):11067-70.
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.
鸡胗肌球蛋白的20,000道尔顿轻链在体外被来自牛心脏的环磷酸腺苷（cAMP）依赖性蛋白激酶（ATP：蛋白磷酸转移酶，EC 2.7.1.37）磷酸化。该酶在一个完全依赖于cAMP且不依赖于Ca2+的反应中，催化每摩尔轻链掺入1摩尔的磷酸根离子（Pi）。使用α-胰凝乳蛋白酶消化产物的二维肽图以及酸性水解产物的磷酸氨基酸分析，来比较cAMP依赖性蛋白激酶磷酸化的位点与火鸡胗肌球蛋白轻链激酶磷酸化的位点。结果表明，两种酶磷酸化的是同一个丝氨酸残基。然而，轻链在体外作为肌球蛋白轻链激酶的底物比作为cAMP依赖性蛋白激酶的底物表现更好。磷酸化丝氨酸周围的氨基酸序列是cAMP依赖性蛋白激酶底物的特征。
