Kuenzel E A, Mulligan J A, Sommercorn J, Krebs E G
J Biol Chem. 1987 Jul 5;262(19):9136-40.
The specificity of casein kinase II has been further defined by analyzing the kinetics of phosphorylation reactions using a number of different synthetic peptides as substrates. The best peptide substrates are those in which multiple acidic amino acids are present on both sides of the phosphorylatable serine or threonine. Acidic residues on the NH2-terminal side of the serine (threonine) greatly enhance the kinetic constants but are not absolutely required. Acidic residues on the COOH-terminal side of the serine (threonine) are absolutely required. One position for which the occupation of an acidic residue is especially critical is the position located 3 residues to the COOH terminus of the phosphate acceptor site, although the presence of an acidic amino acid in the positions that are 4 or 5 residues removed may also provide an appropriate structure that will serve as a substrate for the kinase. Aspartate serves as a better amino acid determinant than glutamate. A relatively short sequence of amino acids surrounding the phosphate acceptor site appears to serve as the basis for the specificity of casein kinase II. The peptides in this study were also assayed with casein kinase I and the casein kinase from the mammary gland so that the specificities of these kinases could be compared to that of casein kinase II.
通过使用多种不同的合成肽作为底物分析磷酸化反应的动力学，进一步明确了酪蛋白激酶II的特异性。最佳的肽底物是那些在可磷酸化的丝氨酸或苏氨酸两侧都存在多个酸性氨基酸的底物。丝氨酸（苏氨酸）氨基末端一侧的酸性残基可大大提高动力学常数，但并非绝对必需。丝氨酸（苏氨酸）羧基末端一侧的酸性残基是绝对必需的。酸性残基占据的一个特别关键的位置是位于磷酸受体位点羧基末端3个残基处的位置，尽管在相隔4个或5个残基的位置存在酸性氨基酸也可能提供一种合适的结构，作为该激酶的底物。天冬氨酸作为氨基酸决定因素比谷氨酸更好。围绕磷酸受体位点的相对较短的氨基酸序列似乎是酪蛋白激酶II特异性的基础。本研究中的肽还用酪蛋白激酶I和来自乳腺的酪蛋白激酶进行了检测，以便将这些激酶的特异性与酪蛋白激酶II的特异性进行比较。
