Kobayashi T, Sadaie M, Ohnishi M, Wang H, Ikeda S, Hanada M, Yanagawa Y, Nakajima T, Tamura S
Institute of Development, Aging and Cancer, Tohoku University, Sendai, 980-8575, Japan.
Biochem Biophys Res Commun. 1998 Oct 9;251(1):296-300. doi: 10.1006/bbrc.1998.9467.
Protein phosphatase 2C (PP2C) is one of the four major protein serine/threonine phosphatases of eukaryotes and is implicated in the regulation of various cellular functions. With the goal of elucidating the mechanism responsible for regulating PP2C functions, we investigated the significance of phosphorylation of fission yeast Ptc1, Ptc2, and Ptc3, the yeast orthologs of mammalian PP2C. Both Ptc2 and Ptc3 but not Ptc1 were phosphorylated stoichiometrically by casein kinase II on serine residues at their carboxy-terminal regions. Mutational analysis of Ptc2 and Ptc3 revealed that serine residues of the conserved sequence (Ser-X-Ser-X-X-Glu/Asp) of these proteins were the phosphorylation sites. Interestingly, the activities of Ptc2 and Ptc3 were decreased 25 +/- 7.5% and increased 55 +/- 3.7%, respectively, by phosphorylation. In addition, the same site(s) of Ptc2 was phosphorylated when the protein was expressed in fission yeast cells. These results suggest that phosphorylation of PP2C plays important physiological roles in fission yeast cells.
蛋白磷酸酶2C（PP2C）是真核生物中四种主要的蛋白丝氨酸/苏氨酸磷酸酶之一，参与多种细胞功能的调节。为了阐明调控PP2C功能的机制，我们研究了裂殖酵母Ptc1、Ptc2和Ptc3（哺乳动物PP2C的酵母同源物）磷酸化的意义。酪蛋白激酶II在Ptc2和Ptc3的羧基末端区域的丝氨酸残基上进行化学计量的磷酸化，而Ptc1未被磷酸化。对Ptc2和Ptc3的突变分析表明，这些蛋白保守序列（Ser-X-Ser-X-X-Glu/Asp）中的丝氨酸残基是磷酸化位点。有趣的是，磷酸化使Ptc2和Ptc3的活性分别降低了25±7.5%和升高了55±3.7%。此外，当该蛋白在裂殖酵母细胞中表达时，Ptc2的相同位点也会被磷酸化。这些结果表明，PP2C的磷酸化在裂殖酵母细胞中发挥重要的生理作用。
