Naka M, Saitoh M, Hidaka H
Department of Molecular and Cellular Pharmacology, Mie University School of Medicine, Japan.
Arch Biochem Biophys. 1988 Mar;261(2):235-40. doi: 10.1016/0003-9861(88)90337-2.
Three forms of 20-kDa myosin light chain (MLC), unphosphorylated, monophosphorylated, and diphosphorylated MLC (designated 20K, 20K-P, and 20K-PP) were demonstrated in thrombin-stimulated human platelets by two different gel electrophoretic methods: in the presence of glycerol urea or in two dimensions (isoelectric and sodium dodecyl sulfate). The diphosphorylation of platelet 20-kDa MLC increased, dose dependently, up to 0.4 U/ml thrombin and reached 25% of platelet 20-kDa MLC. After mono- or diphosphorylated 20-kDa MLC from thrombin-stimulated platelets was digested with trypsin, the analysis using two-dimensional peptide mapping demonstrated that two different sites were phosphorylated by MLC kinase and protein kinase C, as noted in the case of 12-O-tetradecanoylphorbol-13-acetate-stimulated platelets (M. Naka, et al. (1983) Nature (London) 306, 490-492). The more rapid monophosphorylation was catalyzed preferentially by MLC kinase while the slower and additional phosphorylation was catalyzed mainly by protein kinase C. These results suggest the importance of distinguishing multiple site phosphorylation of 20-kDa MLC in thrombin-activated human platelets.
通过两种不同的凝胶电泳方法，在凝血酶刺激的人血小板中证实了三种形式的20 kDa肌球蛋白轻链（MLC），即未磷酸化、单磷酸化和双磷酸化的MLC（分别命名为20K、20K-P和20K-PP）：一种是在甘油尿素存在的情况下，另一种是二维电泳（等电聚焦和十二烷基硫酸钠电泳）。血小板20 kDa MLC的双磷酸化在凝血酶浓度高达0.4 U/ml时呈剂量依赖性增加，达到血小板20 kDa MLC的25%。用胰蛋白酶消化凝血酶刺激的血小板中的单磷酸化或双磷酸化20 kDa MLC后，二维肽图分析表明，如12-O-十四烷酰佛波醇-13-乙酸酯刺激的血小板情况一样（M. 中田等人（1983年）《自然》（伦敦）306, 490 - 492），有两个不同的位点被MLC激酶和蛋白激酶C磷酸化。较快的单磷酸化主要由MLC激酶催化，而较慢的额外磷酸化主要由蛋白激酶C催化。这些结果表明，区分凝血酶激活的人血小板中20 kDa MLC的多位点磷酸化具有重要意义。
