Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3-Phosphoinositide-Dependent Protein Kinases
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Amino Acid Motifs
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Amino Acid Sequence
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Animals
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Binding Sites
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Conserved Sequence
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Enzyme Activation
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Growth Substances / metabolism
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Humans
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Hydrophobic and Hydrophilic Interactions
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Immediate-Early Proteins
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In Vitro Techniques
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Mice
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Models, Molecular
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Molecular Sequence Data
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Nuclear Proteins*
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Phosphorylation
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Phosphoserine / chemistry
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Phosphothreonine / chemistry
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Protein Kinases / chemistry*
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Protein Kinases / genetics
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Protein Kinases / metabolism*
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Protein Serine-Threonine Kinases / chemistry*
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Proto-Oncogene Proteins c-akt
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Proto-Oncogene Proteins*
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Ribosomal Protein S6 Kinases, 90-kDa / chemistry
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Ribosomal Protein S6 Kinases, 90-kDa / genetics
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Ribosomal Protein S6 Kinases, 90-kDa / metabolism
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Sequence Homology, Amino Acid
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Signal Transduction
Substances
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Growth Substances
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Immediate-Early Proteins
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Nuclear Proteins
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Proto-Oncogene Proteins
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Recombinant Proteins
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Phosphothreonine
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Phosphoserine
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Protein Kinases
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3-Phosphoinositide-Dependent Protein Kinases
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PDPK1 protein, human
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Pdpk1 protein, mouse
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Ribosomal Protein S6 Kinases, 90-kDa
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mitogen and stress-activated protein kinase 1
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ribosomal protein S6 kinase, 90kDa, polypeptide 3
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serum-glucocorticoid regulated kinase