Swiderek K, Jaquet K, Meyer H E, Schächtele C, Hofmann F, Heilmeyer L M
Abteilung für Biochemie Supramolekularer Systeme, Ruhr-Universität Bochum, Federal Republic of Germany.
Eur J Biochem. 1990 Jul 5;190(3):575-82. doi: 10.1111/j.1432-1033.1990.tb15612.x.
Bovine cardiac troponin isolated in a highly phosphorylated form shows four 31P-NMR signals [Beier, N., Jaquet, K., Schnackerz, K. & Heilmeyer, L.M.G. Jr (1988) Eur. J. Biochem. 176, 327-334]. Troponin I, which contains phosphate covalently linked to serine-23 and/or -24 [Swiderek, K., Jaquet, K., Meyer, H. E. & Heilmeyer, L. M. G. Jr (1988) Eur. J. Biochem. 176, 335-342], shows three resonances. Mg2(+)-saturation of holotroponin shifts these troponin I resonances to higher fields. Direct binding of Mg2+ to the phosphate groups can be excluded. Both these serine residues of troponin I, 23 and 24, are substrates for cAMP- and cGMP-dependent protein kinases as well as for protein kinase C. Isolated bovine cardiac troponin T contains 1.5 mol phosphoserine/mol protein, indicating that minimally two serine residues are phosphorylated. One phosphoserine residue is located at the N-terminus. An additional phosphoserine is located in the C-terminal cyanogen bromide fragment, CN4, which contains covalently bound phosphate. Protein kinase C phosphorylates serine-194, thus demonstrating exposure of this residue on the surface of holotoponin.
以高度磷酸化形式分离得到的牛心肌肌钙蛋白显示出四个³¹P-NMR信号[Beier, N., Jaquet, K., Schnackerz, K. & Heilmeyer, L.M.G. Jr (1988) Eur. J. Biochem. 176, 327 - 334]。肌钙蛋白I含有与丝氨酸-23和/或-24共价连接的磷酸基团[Swiderek, K., Jaquet, K., Meyer, H. E. & Heilmeyer, L. M. G. Jr (1988) Eur. J. Biochem. 176, 335 - 342]，显示出三个共振峰。全肌钙蛋白的Mg²⁺饱和使这些肌钙蛋白I共振峰向更高场移动。可以排除Mg²⁺与磷酸基团的直接结合。肌钙蛋白I的这两个丝氨酸残基，23和24，都是环磷酸腺苷和环磷酸鸟苷依赖性蛋白激酶以及蛋白激酶C的底物。分离得到的牛心肌肌钙蛋白T含有1.5摩尔磷酸丝氨酸/摩尔蛋白质，这表明至少有两个丝氨酸残基被磷酸化。一个磷酸丝氨酸残基位于N端。另一个磷酸丝氨酸位于C端溴化氰片段CN4中，该片段含有共价结合的磷酸基团。蛋白激酶C使丝氨酸-194磷酸化，从而证明该残基在全肌钙蛋白表面是暴露的。
