Kobayashi T, Kanno S, Terasawa T, Murakami T, Ohnishi M, Ohtsuki K, Hiraga A, Tamura S
Department of Biochemistry, Tohoku University, Sendai, Japan.
Biochem Biophys Res Commun. 1993 Aug 31;195(1):484-9. doi: 10.1006/bbrc.1993.2069.
In this study we show that rat Mg(2+)-dependent protein phosphatase alpha (MPP alpha) expressed in Saccharomyces cerevisiae cells was phosphorylated on serine residues in vivo. The recombinant rat MPP alpha purified from Escherichia coli cells harboring an expression vector was phosphorylated in vitro by casein kinase II, but not by casein kinase I, to 1.5 mol phosphate per mol enzyme protein. Analysis by phosphopeptide mapping and amino acid analysis suggested that the sites of both in vivo and in vitro phosphorylation were the same and involved only serine residues. These results suggest that the rat MPP alpha expressed in yeast cells is phosphorylated by yeast casein kinase II in vivo. It is further proposed that the phosphorylation sites are located in the carboxyl terminal region of the enzyme molecule.
在本研究中，我们发现酿酒酵母细胞中表达的大鼠镁离子依赖蛋白磷酸酶α（MPPα）在体内丝氨酸残基上发生了磷酸化。从携带表达载体的大肠杆菌细胞中纯化得到的重组大鼠MPPα在体外可被酪蛋白激酶II磷酸化，但不能被酪蛋白激酶I磷酸化，每摩尔酶蛋白磷酸化程度达1.5摩尔磷酸盐。磷酸肽图谱分析和氨基酸分析表明，体内和体外磷酸化位点相同，且仅涉及丝氨酸残基。这些结果表明，酵母细胞中表达的大鼠MPPα在体内被酵母酪蛋白激酶II磷酸化。进一步推测磷酸化位点位于酶分子的羧基末端区域。
