Biondi R M, Cheung P C, Casamayor A, Deak M, Currie R A, Alessi D R
Divison of Signal Transduction Therapy, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
EMBO J. 2000 Mar 1;19(5):979-88. doi: 10.1093/emboj/19.5.979.
The 3-phosphoinositide-dependent protein kinase-1 (PDK1) phosphorylates and activates a number of protein kinases of the AGC subfamily. The kinase domain of PDK1 interacts with a region of protein kinase C-related kinase-2 (PRK2), termed the PDK1-interacting fragment (PIF), through a hydrophobic motif. Here we identify a hydrophobic pocket in the small lobe of the PDK1 kinase domain, separate from the ATP- and substrate-binding sites, that interacts with PIF. Mutation of residues predicted to form part of this hydrophobic pocket either abolished or significantly diminished the affinity of PDK1 for PIF. PIF increased the rate at which PDK1 phosphorylated a synthetic dodecapeptide (T308tide), corresponding to the sequences surrounding the PDK1 phosphorylation site of PKB. This peptide is a poor substrate for PDK1, but a peptide comprising T308tide fused to the PDK1-binding motif of PIF was a vastly superior substrate for PDK1. Our results suggest that the PIF-binding pocket on the kinase domain of PDK1 acts as a 'docking site', enabling it to interact with and enhance the phosphorylation of its substrates.
3-磷酸肌醇依赖性蛋白激酶-1（PDK1）可磷酸化并激活AGC亚家族的多种蛋白激酶。PDK1的激酶结构域通过一个疏水基序与蛋白激酶C相关激酶-2（PRK2）的一个区域相互作用，该区域称为PDK1相互作用片段（PIF）。在此，我们在PDK1激酶结构域的小结构域中鉴定出一个疏水口袋，它与ATP和底物结合位点分开，可与PIF相互作用。预测构成该疏水口袋一部分的残基发生突变后，要么消除了PDK1对PIF的亲和力，要么使其显著降低。PIF提高了PDK1磷酸化合成十二肽（T308肽）的速率，该十二肽对应于蛋白激酶B（PKB）的PDK1磷酸化位点周围的序列。该肽是PDK1的不良底物，但包含与PIF的PDK1结合基序融合的T308肽的肽是PDK1的优质得多的底物。我们的结果表明，PDK1激酶结构域上的PIF结合口袋充当“停靠位点”，使其能够与底物相互作用并增强对其底物的磷酸化作用。
