title: Phosphorylation of Ser-241 is essential for the activity of 3-phosphoinositide-dependent protein kinase-1: identification of five sites of phosphorylation in vivo.
abstract: 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.
authors.affiliation: MRC Protein Phosphorylation Unit, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Casamayor
authors.forename: N A
authors.initials: NA
authors.lastname: Morrice
authors.forename: D R
authors.initials: DR
authors.lastname: Alessi
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D014162:Transfection
chemical_list: D011993:Recombinant Fusion Proteins; D012694:Serine; D064413:3-Phosphoinositide-Dependent Protein Kinases; C578562:PDPK1 protein, human; D017346:Protein Serine-Threonine Kinases