Abstract
The type I TGF beta receptor (T beta R-I) is activated by phosphorylation of the GS region, a conserved juxtamembrane segment located just N-terminal to the kinase domain. We have studied the molecular mechanism of receptor activation using a homogeneously tetraphosphorylated form of T beta R-I, prepared using protein semisynthesis. Phosphorylation of the GS region dramatically enhances the specificity of T beta R-I for the critical C-terminal serines of Smad2. In addition, tetraphosphorylated T beta R-I is bound specifically by Smad2 in a phosphorylation-dependent manner and is no longer recognized by the inhibitory protein FKBP12. Thus, phosphorylation activates T beta R-I by switching the GS region from a binding site for an inhibitor into a binding surface for substrate. Our observations suggest that phosphoserine/phosphothreonine-dependent localization is a key feature of the T beta R-I/Smad activation process.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Activin Receptors, Type I*
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Amino Acid Sequence
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Cell Cycle Proteins*
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Checkpoint Kinase 2
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Crystallography, X-Ray
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Immunoblotting
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Models, Biological
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Models, Molecular
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Molecular Sequence Data
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Molecular Structure
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Phosphorylation
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Protein Binding
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Protein Serine-Threonine Kinases / chemical synthesis
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Protein Structure, Secondary
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Protein Structure, Tertiary
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Receptor, Transforming Growth Factor-beta Type I
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Receptors, Transforming Growth Factor beta / genetics
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Receptors, Transforming Growth Factor beta / metabolism*
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae Proteins*
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Smad2 Protein
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Tacrolimus Binding Protein 1A / metabolism
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Trans-Activators / chemistry
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Trans-Activators / genetics
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Trans-Activators / metabolism*
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Transforming Growth Factor beta / antagonists & inhibitors
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Transforming Growth Factor beta / metabolism
Substances
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Cell Cycle Proteins
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DNA-Binding Proteins
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Receptors, Transforming Growth Factor beta
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae Proteins
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Smad2 Protein
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Trans-Activators
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Transforming Growth Factor beta
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Checkpoint Kinase 2
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Protein Serine-Threonine Kinases
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Activin Receptors, Type I
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Receptor, Transforming Growth Factor-beta Type I
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RAD53 protein, S cerevisiae
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Tacrolimus Binding Protein 1A