Ogg S, Gabrielli B, Piwnica-Worms H
Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
J Biol Chem. 1994 Dec 2;269(48):30461-9.
Human Cdc25C is a protein phosphatase that dephosphorylates and activates Cdc2-cyclin B to trigger entry into mitosis. Cdc25C is itself regulated by phosphorylation. In asynchronously growing HeLa cells, we have determined that serine 216 is the major site of Cdc25C phosphorylation. We have isolated a protein kinase that binds to Cdc25C and phosphorylates serine 216. The kinase binds within amino acids 200-256 of Cdc25C. This region is conserved in some Cdc25 homologues and contains a putative bipartite nuclear localization signal just downstream from serine 216. Finally, the Cdc25C-associating kinase was purified over 8000-fold from rat liver as a 36-38-kDa doublet of proteins.
人源Cdc25C是一种蛋白磷酸酶，它通过去磷酸化作用激活Cdc2-细胞周期蛋白B，从而触发细胞进入有丝分裂。Cdc25C自身受磷酸化作用调控。在异步生长的HeLa细胞中，我们已确定丝氨酸216是Cdc25C磷酸化的主要位点。我们分离出一种与Cdc25C结合并使丝氨酸216磷酸化的蛋白激酶。该激酶结合在Cdc25C的200-256位氨基酸内。此区域在一些Cdc25同源物中保守，且在丝氨酸216下游含有一个假定的双分型核定位信号。最后，从大鼠肝脏中纯化出与Cdc25C相关的激酶，纯化倍数超过8000倍，得到一种36-38 kDa的双蛋白条带。
