Casamayor A, Morrice N A, Alessi D R
MRC Protein Phosphorylation Unit, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
Biochem J. 1999 Sep 1;342 ( Pt 2)(Pt 2):287-92.
3-phosphoinositide-dependent protein kinase-1 (PDK1) expressed in unstimulated 293 cells was phosphorylated at Ser-25, Ser-241, Ser-393, Ser-396 and Ser-410 and the level of phosphorylation of each site was unaffected by stimulation with insulin-like growth factor-1. Mutation of Ser-241 to Ala abolished PDK1 activity, whereas mutation of the other phosphorylation sites individually to Ala did not affect PDK1 activity. Ser-241, unlike the other phosphorylation sites on PDK1, was resistant to dephosphorylation by protein phosphatase 2A(1). Ser-241 lies in the activation loop of the PDK1 kinase domain between subdomains VII and VIII in the equivalent position to the site that PDK1 phosphorylates on its protein kinase substrates. PDK1 expressed in bacteria was active and phosphorylated at Ser-241, suggesting that PDK1 can phosphorylate itself at this site, leading to its own activation.
在未受刺激的293细胞中表达的3-磷酸肌醇依赖性蛋白激酶-1（PDK1）在丝氨酸-25、丝氨酸-241、丝氨酸-393、丝氨酸-396和丝氨酸-410处发生磷酸化，并且每个位点的磷酸化水平不受胰岛素样生长因子-1刺激的影响。将丝氨酸-241突变为丙氨酸会消除PDK1活性，而将其他磷酸化位点分别突变为丙氨酸则不影响PDK1活性。与PDK1上的其他磷酸化位点不同，丝氨酸-241对蛋白磷酸酶2A的去磷酸化具有抗性。丝氨酸-241位于PDK1激酶结构域的激活环中，在亚结构域VII和VIII之间，与PDK1在其蛋白激酶底物上磷酸化的位点处于等效位置。在细菌中表达的PDK1具有活性并且在丝氨酸-241处发生磷酸化，这表明PDK1可以在该位点自身磷酸化，从而导致其自身激活。
