A phosphorylation-dependent gating mechanism controls the SH2 domain interactions of the Shc adaptor protein.
The Shc (Src homology collagen-like) adaptor protein plays a crucial role in linking stimulated receptors to mitogen-activated protein kinase activation through the formation of dynamic signalling complexes. Shc comprises an N-terminal phosphotyrosine binding (PTB) domain, a C-terminal Src homology 2 (SH2) domain and a central proline-rich collagen homology 1 domain. The latter domain contains three tyrosine residues that are known to become phosphorylated. We have expressed and purified the human p52Shc isoform and characterised its binding to different ligands. CD spectra revealed that some parts of the Shc protein are not fully folded, remaining largely unaffected by the binding of ligands. The PTB domain binds peptide and Ins-1,4,5-P(3) (but not Ins-1,3,5-P(3)) independently, suggesting two distinct sites of interaction. In the unphosphorylated Shc, the SH2 domain is non-functional. Ligand binding to the PTB domain does not affect this. However, phosphorylation of the three tyrosine residues promotes binding to the SH2 domain. Thus, Shc has an intrinsic phosphorylation-dependent gating mechanism where the SH2 domain adopts an open conformation only when tyrosine phosphorylation has occurred.
George
Roger
R
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK.
Schuller
Annika C
AC
Harris
Richard
R
Ladbury
John E
JE
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008024:Ligands; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D008024:Ligands; D010455:Peptides; D020033:Protein Isoforms; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D015544:Inositol 1,4,5-Trisphosphate