Edelman A M, Lin W H, Osterhout D J, Bennett M K, Kennedy M B, Krebs E G
Department of Pharmacology and Therapeutics, School of Medicine and Biomedical Sciences, State University of New York, Buffalo 14214.
Mol Cell Biochem. 1990 Sep 3;97(1):87-98. doi: 10.1007/BF00231704.
Brain type II Ca2+/calmodulin-dependent protein kinase was found to phosphorylate smooth muscle myosin, incorporating maximally approximately 2 mol of phosphoryl per mol of myosin, exclusively on the 20,000 dalton light chain subunit. After maximal phosphorylation of myosin or the isolated 20,000 dalton light chain subunit by myosin light chain kinase, the addition of type II Ca2+/calmodulin-dependent protein kinase led to no further incorporation indicating the two kinases phosphorylated a common site. This conclusion was supported by two dimensional mapping of tryptic digests of myosin phosphorylated by the two kinases. By phosphoamino acid analysis the phosphorylated residue was identified as a serine. The phosphorylation by type II Ca2+/calmodulin-dependent protein kinase of myosin resulted in enhancement of its actin-activated Mg2(+)-ATPase activity. Taken together, these data strongly support the conclusion that type II Ca2+/calmodulin-dependent protein kinase phosphorylates the same amino acid residue on the 20,000 dalton light chain subunit of smooth muscle myosin as is phosphorylated by myosin light chain kinase and suggest an alternative mechanism for the regulation of actin-myosin interaction.
已发现脑II型钙调蛋白依赖性蛋白激酶可使平滑肌肌球蛋白磷酸化，每摩尔肌球蛋白最多掺入约2摩尔磷酰基，且仅在20,000道尔顿轻链亚基上。在用肌球蛋白轻链激酶使肌球蛋白或分离出的20,000道尔顿轻链亚基最大程度磷酸化后，加入II型钙调蛋白依赖性蛋白激酶不会导致进一步掺入，这表明这两种激酶磷酸化的是同一个位点。这一结论得到了两种激酶磷酸化的肌球蛋白胰蛋白酶消化产物二维图谱的支持。通过磷酸氨基酸分析，确定磷酸化残基为丝氨酸。II型钙调蛋白依赖性蛋白激酶对肌球蛋白的磷酸化导致其肌动蛋白激活的Mg2(+)-ATP酶活性增强。综上所述，这些数据有力地支持了这样的结论：II型钙调蛋白依赖性蛋白激酶与肌球蛋白轻链激酶磷酸化平滑肌肌球蛋白20,000道尔顿轻链亚基上的同一个氨基酸残基，并提示了一种调节肌动蛋白-肌球蛋白相互作用的替代机制。
