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Title
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Specificity of the PTB domain of Shc for beta turn-forming pentapeptide motifs amino-terminal to phosphotyrosine.
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Authors
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T.Trüb,
W.E.Choi,
G.Wolf,
E.Ottinger,
Y.Chen,
M.Weiss,
S.E.Shoelson.
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Ref.
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J Biol Chem, 1995,
270,
18205-18208.
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PubMed id
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Abstract
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Shc phosphorylation in cells following growth factor, insulin, cytokine, and
lymphocyte receptor activation leads to its association with Grb2 and activation
of Ras. In addition to being a cytoplasmic substrate of tyrosine kinases, Shc
contains an SH2 domain and a non-SH2 phosphotyrosine binding (PTB) domain. Here
we show that the Shc PTB domain, but not the SH2 domain, binds with high
affinity (ID50 approximately equal to 1 microM) to phosphopeptides corresponding
to the sequence surrounding Tyr250 of the polyoma virus middle T (mT) antigen
(LLSNPTpYSVMRSK). Truncation studies show that five residues amino-terminal to
tyrosine are required for high affinity binding, whereas all residues
carboxyl-terminal to tyrosine can be deleted without loss of affinity.
Substitution studies show that tyrosine phosphorylation is required and residues
at -5, -3, -2, and -1 positions relative to pTyr are important for this
interaction. 1H NMR studies demonstrate that the phosphorylated mT
antigen-derived sequence forms a stable beta turn in solution, and correlations
between structure and function indicate that the beta turn is important for PTB
domain recognition. These results show that PTB domains are functionally
distinct from SH2 domains. Whereas SH2 domain binding specificity derives from
peptide sequences carboxyl-terminal to phosphotyrosine, the Shc PTB domain gains
specificity by interacting with beta turn-forming sequences amino-terminal to
phosphotyrosine.
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