A phosphoserine/threonine-binding pocket in AGC kinases and PDK1 mediates activation by hydrophobic motif phosphorylation.
The growth factor-activated AGC protein kinases RSK, S6K, PKB, MSK and SGK are activated by serine/threonine phosphorylation in the activation loop and in the hydrophobic motif, C-terminal to the kinase domain. In some of these kinases, phosphorylation of the hydrophobic motif creates a specific docking site that recruits and activates PDK1, which then phosphorylates the activation loop. Here, we discover a pocket in the kinase domain of PDK1 that recognizes the phosphoserine/phosphothreonine in the hydrophobic motif by identifying two oppositely positioned arginine and lysine residues that bind the phosphate. Moreover, we demonstrate that RSK2, S6K1, PKBalpha, MSK1 and SGK1 contain a similar phosphate-binding pocket, which they use for intramolecular interaction with their own phosphorylated hydrophobic motif. Molecular modelling and experimental data provide evidence for a common activation mechanism in which the phosphorylated hydrophobic motif and activation loop act on the alphaC-helix of the kinase structure to induce synergistic stimulation of catalytic activity. Sequence conservation suggests that this mechanism is a key feature in activation of >40 human AGC kinases.
Frödin
Morten
M
Department of Clinical Biochemistry, Glostrup Hospital, DK-2600 Glostrup, Denmark. mf@dcb-glostrup.dk
Antal
Torben L
TL
Dümmler
Bettina A
BA
Jensen
Claus J
CJ
Deak
Maria
M
Gammeltoft
Steen
S
Biondi
Ricardo M
RM
D064413:3-Phosphoinositide-Dependent Protein Kinases; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017124:Conserved Sequence; D004789:Enzyme Activation; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D017874:Immediate-Early Proteins; D066298:In Vitro Techniques; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010766:Phosphorylation; D010768:Phosphoserine / Q000737:chemistry; D010769:Phosphothreonine / Q000737:chemistry; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D000099184:Serum-Glucocorticoid Regulated Kinases
D064413:3-Phosphoinositide-Dependent Protein Kinases; D006133:Growth Substances; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D010768:Phosphoserine; D010769:Phosphothreonine; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D000099184:Serum-Glucocorticoid Regulated Kinases; C578562:PDPK1 protein, human; C578564:Pdpk1 protein, mouse; C116919:mitogen and stress-activated protein kinase 1; C069330:ribosomal protein S6 kinase, 90kDa, polypeptide 3