Phosphotyrosine Binding Domains of Shc and Insulin Receptor Substrate 1 Recognize the NPXpY Motif in a Thermodynamically Distinct Manner

Abstract

Phosphotyrosine binding (PTB) domains of the adaptor protein Shc and insulin receptor substrate (IRS-1) interact with a distinct set of activated and tyrosine-phosphorylated cytokine and growth factor receptors and play important roles in mediating mitogenic signal transduction. By using the technique of isothermal titration calorimetry, we have studied the thermodynamics of binding of the Shc and IRS-1 PTB domains to tyrosine-phosphorylated NPXY-containing peptides derived from known receptor binding sites. The results showed that relative contributions of enthalpy and entropy to the free energy of binding are dependent on specific phosphopeptides. Binding of the Shc PTB domain to tyrosine-phosphorylated peptides from TrkA, epidermal growth factor, ErbB3, and insulin receptors is achieved via an overall entropy-driven reaction. On the other hand, recognition of the phosphopeptides of insulin and interleukin-4 receptors by the IRS-1 PTB domain is predominantly an enthalpy-driven process. Mutagenesis and amino acid substitution experiments showed that in addition to the tyrosine-phosphorylated NPXY motif, the PTB domains of Shc and IRS-1 prefer a large hydrophobic residue at pY-5 and a small hydrophobic residue at pY-1, respectively (where pY is phosphotyrosine). These results agree with the calculated solvent accessibility of these two key peptide residues in the PTB domain/peptide structures and support the notion that the PTB domains of Shc and IRS-1 employ functionally distinct mechanisms to recognize tyrosine-phosphorylated receptors. Phosphotyrosine binding (PTB) domains of the adaptor protein Shc and insulin receptor substrate (IRS-1) interact with a distinct set of activated and tyrosine-phosphorylated cytokine and growth factor receptors and play important roles in mediating mitogenic signal transduction. By using the technique of isothermal titration calorimetry, we have studied the thermodynamics of binding of the Shc and IRS-1 PTB domains to tyrosine-phosphorylated NPXY-containing peptides derived from known receptor binding sites. The results showed that relative contributions of enthalpy and entropy to the free energy of binding are dependent on specific phosphopeptides. Binding of the Shc PTB domain to tyrosine-phosphorylated peptides from TrkA, epidermal growth factor, ErbB3, and insulin receptors is achieved via an overall entropy-driven reaction. On the other hand, recognition of the phosphopeptides of insulin and interleukin-4 receptors by the IRS-1 PTB domain is predominantly an enthalpy-driven process. Mutagenesis and amino acid substitution experiments showed that in addition to the tyrosine-phosphorylated NPXY motif, the PTB domains of Shc and IRS-1 prefer a large hydrophobic residue at pY-5 and a small hydrophobic residue at pY-1, respectively (where pY is phosphotyrosine). These results agree with the calculated solvent accessibility of these two key peptide residues in the PTB domain/peptide structures and support the notion that the PTB domains of Shc and IRS-1 employ functionally distinct mechanisms to recognize tyrosine-phosphorylated receptors. Protein tyrosine phosphorylation provides a central control mechanism in regulating protein-protein interactions and activation of enzymes in mitogenic signal transduction following activation of cytokine and growth factor receptors (1Hunter T. Cell. 1995; 80: 225-236Abstract Full Text PDF PubMed Scopus (2604) Google Scholar, 2Pawson T. Nature. 1995; 373: 573-580Crossref PubMed Scopus (2229) Google Scholar). Key events in receptor signaling are the interactions of signaling molecules such as adaptor protein Shc and insulin receptor substrate (IRS-1) 1The abbreviations used are: IRS-1, insulin receptor substrate 1; IR, insulin receptor; IL-4R, interleukin-4 receptor; ITC, isothermal titration calorimetry; NTA, nitrilotriacetic acid; pY, phosphotyrosine; PTB, phosphotyrosine binding; SASA, solvent-accessible surface area; SH2 Src homology-2, Fmoc,N-(9-fluorenyl)methoxycarbonyl; EGF, epidermal growth factor; PH, pleckstrin homology. with activated and tyrosine-phosphorylated receptors. Binding to the activated receptor results in tyrosine phosphorylation of these signaling molecules, which in turn experience specific interactions with downstream signaling proteins and/or enzymes. For example, in insulin receptor (IR) signaling, upon binding to the activated receptor, IRS-1 is phosphorylated on many tyrosine residues, which enables IRS-1 to interact with various Src homology 2 (SH2) domain-containing proteins, including phosphatidylinositol 3-kinase, protein tyrosine phosphatase SH-PTP2, and Grb2 (3Sun X.J. Crimmins D.L. Myers M.G.J. Miralpeix M. White M.F. Mol. Cell. Biol. 1993; 13: 7418-7428Crossref PubMed Google Scholar). On the other hand, tyrosine-phosphorylated Shc interacts with the SH2 domain of the adaptor protein Grb2, which in turn binds via its Src homology 3 (SH3) domains to the guanine nucleotide exchange factor, SOS, leading to Ras activation (4Salcini A. McGlade J. Pelicci G. Nicoletti I. Pawson T. Pelicci P. Oncogene. 1994; 9: 2827-2836PubMed Google Scholar, 5Rozakis-Adcock M. McGlade J. Mbamalu G. Pelicci G. Daly R. Li W. Batzer A. Thoma S. Brugge J. Pelicci P.G. Schlessinger J. Pawson T. Nature. 1992; 360: 689-692Crossref PubMed Scopus (827) Google Scholar). Both IRS-1 and Shc can bind to the activated and tyrosine-phosphorylated insulin receptor through their phosphotyrosine binding (PTB) domain (also called PID or SAIN domain) (6Gustafson T.A. He W. Craparo A. Schaub C.D. O'Meill T.J. Mol. Cell. Biol. 1995; 15: 2500-2508Crossref PubMed Scopus (327) Google Scholar). The PTB domain is a recently recognized protein module that can serve as an alternative to the SH2 domain for binding to tyrosine-phosphorylated proteins (6Gustafson T.A. He W. Craparo A. Schaub C.D. O'Meill T.J. Mol. Cell. Biol. 1995; 15: 2500-2508Crossref PubMed Scopus (327) Google Scholar, 7Kavanaugh W.M. Williams L.T. Science. 1994; 266: 1862-1865Crossref PubMed Scopus (451) Google Scholar, 8Blaikie P. Immanuel D. Wu J. Li N. Yajnik V. Margolis B. J. Biol. Chem. 1994; 269: 32031-32034Abstract Full Text PDF PubMed Google Scholar, 9Geer P.V.D. Wiley S. Lai K. Olivier J. Gish G. Stephens R. Kaplan D. Shoelson S. Pawson T. Curr. Biol. 1995; 5: 404-412Abstract Full Text Full Text PDF PubMed Scopus (156) Google Scholar). PTB domains that are structurally and functionally distinct from SH2 domains recognize amino acid residues N-terminal (rather than C-terminal) to the phosphotyrosine (pY) (2Pawson T. Nature. 1995; 373: 573-580Crossref PubMed Scopus (2229) Google Scholar, 10Cohen G.B. Ren R. Baltimore D. Cell. 1995; 80: 237-248Abstract Full Text PDF PubMed Scopus (925) Google Scholar, 11Zhou M.-M. Fesik S.W. Prog. Biophys. Mol. Biol. 1995; 64: 221-235Crossref PubMed Scopus (20) Google Scholar). In particular, PTB domains preferentially bind to phosphorylated proteins at sites containing a NPXpY motif and hydrophobic amino acids N-terminal to this sequence (12Trüb T. Cho W.E. Wolf G. Ottinger E. Hen Y. Weiss M. Shoelson S.E. J. Biol. Chem. 1995; 270: 18205-18208Abstract Full Text Full Text PDF PubMed Scopus (88) Google Scholar, 13Kavanaugh W.M. Turck C.W. Williams L.T. Science. 1995; 268: 1177-1179Crossref PubMed Scopus (223) Google Scholar, 14Zhou S. Margolis B. Chaudhuri M. Shoelson S.E. Cantley L.C. J. Biol. Chem. 1995; 270: 14863-14866Crossref PubMed Scopus (159) Google Scholar, 15Wolf G. Trüb T. Ottinger E. Groninga L. Lynch A. White M.F. Miyazaki M. Lee J. Shoelson S.E. J. Biol. Chem. 1995; 270: 27407-27410Abstract Full Text Full Text PDF PubMed Scopus (208) Google Scholar). Unlike SH2 domains, PTB domains show very low protein sequence homology. Different PTB domains exhibit distinct selectivity for residues N-terminal to the NPXpY-motif. For example, the IRS-1 PTB domain favors hydrophobic residues at the pY-6 and pY-8 positions and an Ala at pY-1 for high affinity binding (15Wolf G. Trüb T. Ottinger E. Groninga L. Lynch A. White M.F. Miyazaki M. Lee J. Shoelson S.E. J. Biol. Chem. 1995; 270: 27407-27410Abstract Full Text Full Text PDF PubMed Scopus (208) Google Scholar, 16He W. O;Neill T.J. Gustafson T.A. J. Biol. Chem. 1995; 270: 23258-23262Crossref PubMed Scopus (85) Google Scholar), whereas the Shc PTB domain requires a bulky hydrophobic residue at pY-5 (12Trüb T. Cho W.E. Wolf G. Ottinger E. Hen Y. Weiss M. Shoelson S.E. J. Biol. Chem. 1995; 270: 18205-18208Abstract Full Text Full Text PDF PubMed Scopus (88) Google Scholar, 13Kavanaugh W.M. Turck C.W. Williams L.T. Science. 1995; 268: 1177-1179Crossref PubMed Scopus (223) Google Scholar, 14Zhou S. Margolis B. Chaudhuri M. Shoelson S.E. Cantley L.C. J. Biol. Chem. 1995; 270: 14863-14866Crossref PubMed Scopus (159) Google Scholar). Recent structural analysis revealed that the two PTB domains are structurally related but employ two very different mechanisms for recognizing the phosphotyrosine and the hydrophobic residues N-terminal to the NPXpY sequence (17Zhou M.-M. Ravichandran K.S. Olejniczak E.T. Petros A.P. Meadows R.P. Sattler M. Harlan J.E. Wade W. Burakoff S.J. Fesik S.W. Nature. 1995; 378: 584-592Crossref PubMed Scopus (324) Google Scholar, 18Zhou M.-M. B. Olejniczak E.T. Meadows R.P. M. Trüb T. Shoelson S.E. Fesik S.W. Biol. PubMed Scopus Google Scholar, S. Trüb T. R. Shoelson S.E. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). for the insulin receptor (6Gustafson T.A. He W. Craparo A. Schaub C.D. O'Meill T.J. Mol. Cell. Biol. 1995; 15: 2500-2508Crossref PubMed Scopus (327) Google Scholar), the PTB domains of Shc and IRS-1 have to interact with a distinct set of growth factor and cytokine receptors. For example, the Shc PTB domain binds to activated and tyrosine-phosphorylated TrkA, ErbB3, and epidermal growth factor receptors G. L. McGlade J. G. Nicoletti I. Pawson T. Cell. 1992; Full Text PDF PubMed Scopus Google Scholar, A. R. K. G. Schlessinger J. A. J. Biol. Chem. 1993; 268: Full Text PDF PubMed Google Scholar, A. L. R. G. P.G. Pelicci P.G. Oncogene. 1995; Google Scholar), whereas IRS-1 interacts with the tyrosine-phosphorylated interleukin-4 receptor via its PTB domain Myers M.G.J. X.J. White M. Science. 1993; PubMed Scopus Google Scholar, K. White M. W.E. Cell. 1994; Full Text PDF PubMed Scopus Google Scholar). of thermodynamics of interactions can important the structural and of recognition of the In an to the structural and of in the mechanisms by which the Shc and IRS-1 PTB domains recognize tyrosine-phosphorylated we have studied thermodynamics of peptide binding of the PTB domains using the isothermal titration The phosphopeptides used in this derived from known and sites on growth factor and cytokine receptors. from these revealed that the PTB domains of Shc and IRS-1 to bind in a distinct to the The of the free energy of the interactions show that the high affinity binding of the Shc PTB domain to the phosphopeptides is an overall entropy-driven process. In recognition of the IRS-1 PTB domain to the and phosphopeptides is achieved predominantly by a large enthalpy By using and amino acid we have the relative of the pY-5 and pY-1 residues in binding to the PTB The PTB domain of Shc and using as (17Zhou M.-M. Ravichandran K.S. Olejniczak E.T. Petros A.P. Meadows R.P. Sattler M. Harlan J.E. Wade W. Burakoff S.J. Fesik S.W. Nature. 1995; 378: 584-592Crossref PubMed Scopus (324) Google Scholar, M.-M. Harlan J.E. Wade W. S. Ravichandran K.S. Burakoff S.J. Fesik S.W. J. Biol. Chem. 1995; 270: PubMed Scopus Google Scholar). the protein the which a by a at the of the The protein in which with for at The protein by affinity on a and with to the The PTB domain of IRS-1 used in this of residues of the protein and in E. with an sequence at the as M.-M. B. Olejniczak E.T. Meadows R.P. M. Trüb T. Shoelson S.E. Fesik S.W. Biol. PubMed Scopus Google Scholar). The in and the of the protein using at for The using a The protein by a of this protein with at a the and the amino acids to the PTB domain of IRS-1 The IRS-1 PTB Ala as using the Mutagenesis and the used in the M.-M. B. Olejniczak E.T. Meadows R.P. M. Trüb T. Shoelson S.E. Fesik S.W. Biol. PubMed Scopus Google Scholar). and of the IRS-1 PTB domain as for the The tyrosine-phosphorylated peptides used in the experiments by the Protein at the of using an Phosphotyrosine using the with of the peptides by high with an T. S. PubMed Scopus Google Scholar). experiments at in a of containing and for protein of the PTB domains of Shc and IRS-1, as of protein for to protein as by Both the PTB domains and the phosphopeptides in the The of protein and of and the the in the of for the for the binding of the IRS-1 PTB domain to the phosphopeptides of and for binding of the Shc PTB domain to phosphopeptides at and pY of the in experiments for at different protein The for and calculated from the of the titration to a on the binding of a to a A. L. R. G. P.G. Pelicci P.G. Oncogene. 1995; Google Scholar), using In this the and to The to and are from the whereas and are in a The of the in experiments for at different protein The for and calculated from the of the titration to a on the binding of a to a A. L. R. G. P.G. Pelicci P.G. Oncogene. 1995; Google Scholar), using In this the and to The to and are from the whereas and are titration of of a peptide the containing of a protein and an at the of the for of the protein and the the In the to with the enthalpy of the binding of the to the PTB The of the enthalpy of of the protein from titration to The peptide whereas the protein using the to an by a using the is upon the binding of a to a T. S. PubMed Scopus Google and and as the These can from the of and the free energy and entropy upon peptide binding can calculated using the the and is the at on a proteins of the IRS-1 PTB domain for the experiments by that the PTB domain in an containing as the The of and the Ala of the IRS-1 PTB domain at a of in of containing and in with and in and The and using the S. G. J. A. J. 1995; PubMed Scopus Google and J. 1994; PubMed Scopus Google used the receptor peptide in the isothermal titration as the used in structural analysis of the Shc PTB by (17Zhou M.-M. Ravichandran K.S. Olejniczak E.T. Petros A.P. Meadows R.P. Sattler M. Harlan J.E. Wade W. Burakoff S.J. Fesik S.W. Nature. 1995; 378: 584-592Crossref PubMed Scopus (324) Google Scholar). a peptide titration using ITC, can of the binding Nature. PubMed Scopus Google Scholar, J.E. M. J. Schlessinger J. S. A. 1995; PubMed Scopus Google Scholar). The binding binding enthalpy of binding and free energy by a of the binding as as entropy of binding from a the and the enthalpy of and the titration of the Shc PTB domain binding to the peptide show that a is with the peptide that the is at The upon addition of the to the protein a at of the protein to that the Shc PTB domain binding to the peptide is very and the of this is By using these we calculated a to the titration revealed that the high affinity binding of the Shc PTB domain to the peptide is achieved by an overall entropy-driven as the free energy of binding results predominantly from a large titration for binding of the Shc PTB domain to and the IRS-1 PTB domain to tyrosine-phosphorylated peptides of and The show the of the to a on the binding of a to a using the T. S. PubMed Scopus Google the Shc PTB domain interacts with other we of the Shc PTB domain binding to tyrosine-phosphorylated peptides derived from EGF, ErbB3, and insulin receptors The results that the enthalpy of binding or is of entropy favors the this large to the for the high affinity of the Shc PTB domain binding to the phosphopeptides. is with the phosphopeptides that the sequence of (where pY-5 is a hydrophobic known for the high affinity binding to the Shc PTB domain but with the that large hydrophobic residues at pY-6 to pY-8 of the thermodynamics of the PTB domain of Shc binding to tyrosine-phosphorylated we using a derived from receptor is a for the Shc PTB domain as Shc to On the other hand, the peptide a binding for the IRS-1 PTB domain Myers M.G.J. X.J. White M. Science. 1993; PubMed Scopus Google Scholar, K. White M. W.E. Cell. 1994; Full Text PDF PubMed Scopus Google Scholar). The results showed that the PTB domain of Shc binds to the peptide than to phosphopeptides from the known Shc binding sites the Shc binding of the peptide is by a large results that the of binding of the Shc PTB domain to the phosphopeptides of the TrkA, EGF, ErbB3, and insulin receptors to an overall entropy-driven process. an titration using a from the which is a known binding for IRS-1 Myers M.G.J. X.J. White M. Science. 1993; PubMed Scopus Google Scholar, K. White M. W.E. Cell. 1994; Full Text PDF PubMed Scopus Google Scholar). in binding of the IRS-1 PTB domain to the peptide is and an of entropy of the a of for this PTB the peptide with the IRS-1 PTB domain is which is in to the entropy-driven binding of the Shc PTB for binding of the IRS-1 PTB domain to phosphopeptides at and pY the signal is to the signal is to the signal is to of the in and I. The for to for and are from the whereas and are These the signal is to in a The of the in and I. The for to for and are from the whereas and are Binding of the IRS-1 PTB domain to the peptide to by an enthalpy binding affinity of the peptide to the IRS-1 PTB domain is than that of the peptide of the peptide binding affinity with an entropy The in amino acid sequence the and phosphopeptides is the residue at the of the pY-1 residue to binding of the IRS-1 PTB we the pY-1 in the peptide by an The amino acid to the Ala pY-1 in the The showed that this amino acid substitution to a of the binding affinity to and which is the as that of the peptide binding to the IRS-1 PTB domain is to that this of the peptide binding affinity results from a of the entropy of the of the peptide showed with the protein as by isothermal titration that binding of the IRS-1 PTB domain to the motif is tyrosine the of the hydrophobic residue at pY-1, we the pY-1 by amino acid or in the The showed that the containing or at pY-1 binds to the IRS-1 PTB domain than the but than the which a at The for a small hydrophobic residue at pY-1 by the IRS-1 PTB domain with structural analysis of the PTB peptide M.-M. B. Olejniczak E.T. Meadows R.P. M. Trüb T. Shoelson S.E. Fesik S.W. Biol. PubMed Scopus Google Scholar). The revealed that the Ala pY-1 in the motif interacts with a hydrophobic binding by and the relative of this hydrophobic to we of the IRS-1 PTB domain to Ala for of the Ala and IRS-1 PTB domain that the structural and The binding affinity of this to and peptides an of than that of the protein The of an Ala at pY-1 for high affinity binding to the IRS-1 PTB amino acid residues at this are in the known Shc PTB domain binding sites in various mitogenic receptors. the PTB domain of Shc a large hydrophobic residue at pY-5 as by structural analysis of the Shc PTB peptide (17Zhou M.-M. Ravichandran K.S. Olejniczak E.T. Petros A.P. Meadows R.P. Sattler M. Harlan J.E. Wade W. Burakoff S.J. Fesik S.W. Nature. 1995; 378: 584-592Crossref PubMed Scopus (324) Google Scholar). The revealed that in addition to the NPXpY motif, the pY-5 of the peptide interacts with residues in the hydrophobic of the PTB domain of the of the pY-5 to the high affinity peptide we Ala for pY-5 in the The showed that this substitution results in a in the peptide binding affinity as with the binding of the peptide showed enthalpy and entropy of binding to and the peptide binding to the Shc PTB domain is an entropy-driven process. the of a large hydrophobic residue at pY-5 is specific for the Shc PTB we the of the IRS-1 PTB domain binding to the tyrosine-phosphorylated peptides derived from known Shc PTB domain binding sites on TrkA, EGF, and receptors. The revealed that these peptides showed very or binding to the IRS-1 PTB domain can by the IRS-1 PTB domain M.-M. B. Olejniczak E.T. Meadows R.P. M. Trüb T. Shoelson S.E. Fesik S.W. Biol. PubMed Scopus Google Scholar), which is in the PTB domain to hydrophobic at pY-5 in the phosphopeptides. These which agree with structural and (12Trüb T. Cho W.E. Wolf G. Ottinger E. Hen Y. Weiss M. Shoelson S.E. J. Biol. Chem. 1995; 270: 18205-18208Abstract Full Text Full Text PDF PubMed Scopus (88) Google Scholar, M.-M. Ravichandran K.S. Olejniczak E.T. Petros A.P. Meadows R.P. Sattler M. Harlan J.E. Wade W. Burakoff S.J. Fesik S.W. Nature. 1995; 378: 584-592Crossref PubMed Scopus (324) Google Scholar), that in addition to the NPXpY motif, the PTB domains of Shc and IRS-1 recognize specific amino acid residues N-terminal to the pY in to their distinct binding the of hydrophobic interactions the PTB domains and we calculated solvent-accessible surface for the residues in the PTB The results that the of the solvent accessibility of the residues with the of their interactions with the PTB domains and For example, the Ala pY-1 of the peptide is in the IRS-1 PTB peptide as its calculated in the PTB is that in a is in with the of the Ala pY-1 in the peptide binding and binding affinity of the IRS-1 PTB The analysis of the IRS-1 PTB domain revealed that and that are in interactions with the Ala pY-1 are with than peptide residues important for binding to the PTB domain show low SASA, such as for and for Ala The of the pY and the hydrophobic residues at pY-6 and is and These results are with the PTB domain which that the binding sites for these peptide residues are on the surface of the the analysis of the Shc PTB domain 3 that the peptide residues of the pY, and are in interactions with the In this we have the thermodynamics of binding of the PTB domains of Shc and IRS-1 to the NPXpY phosphopeptides. results that the binding of IRS-1 PTB domain to tyrosine-phosphorylated and peptides is an enthalpy-driven whereas the binding of Shc PTB domain to tyrosine-phosphorylated peptides of TrkA, EGF, ErbB3, and insulin receptors to by the phosphopeptides used in this are derived from known and sites in cytokine and growth factor results the of interactions of the PTB domains with the tyrosine-phosphorylated receptors. that V. R. M. Margolis B. Schlessinger J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google have recently of the Shc PTB domain binding to phosphopeptides from and receptors. and V. R. M. Margolis B. Schlessinger J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google of of and of for the peptide and a of of and of for the receptor agree with their results of the peptide in but from of the receptor peptide The the two to in the used in the The used in for these two phosphopeptides and which are to for the T. S. PubMed Scopus Google Scholar), whereas their in the of The enthalpy-driven of the IRS-1 PTB domain binding to the tyrosine-phosphorylated peptides is with the and protein of the IRS-1 PTB peptide M.-M. B. Olejniczak E.T. Meadows R.P. M. Trüb T. Shoelson S.E. Fesik S.W. Biol. PubMed Scopus Google Scholar). of hydrophobic and and the protein and peptide residues for the in the On the other hand, the in the peptide binding from the a of entropy of amino acid residues that are in the peptide binding and upon the and a of entropy of the protein and peptide molecules upon By using we have recently the of the of the IRS-1 PTB domain in the free protein and the protein to the E.T. M.-M. Fesik S.W. PubMed Scopus Google Scholar). The results showed that the of residues including a residues that with the in the of these residues upon binding to of the entropy of the is to that the of entropy in the IRS-1 PTB domain binding to the peptide to agree with the recently entropy for protein-protein that using the from A. J. Mol. Biol. PubMed Scopus Google Scholar). these results that the of the IRS-1 PTB domain binding to the peptide from the of the entropy of the binding of the Shc PTB domain different from that of the IRS-1 PTB The of the Shc PTB using its The of the Shc PTB peptide showed that the PTB domain interacts with peptide residues than the IRS-1 PTB Shc binding affinity in the contributions of enthalpy and entropy to the free energy of binding on PTB domain interactions with specific the high affinity peptide binding to the Shc PTB domain is achieved by a large entropy entropy-driven of the binding that the binding of the Shc PTB domain to the peptides the of hydrophobic surface and/or an in the of the protein upon The of hydrophobic surface of a protein upon binding to its can by of the of which can from enthalpy of binding at different Science. 1994; PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). By using the we the of the IRS-1 PTB domain binding to the peptide to this is very to the by V. R. M. Margolis B. Schlessinger J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google for the Shc PTB domain binding to the and receptor that an analysis of the of hydrophobic surface using the J.E. J. Mol. Biol. 1994; PubMed Scopus Google Scholar). these that the of hydrophobic surface upon binding for the PTB domains of Shc and the contributions in the Shc PTB domain binding to the phosphopeptides from an in the of the protein upon recently structural of the Shc PTB domain of the free that the protein upon binding to the tyrosine-phosphorylated and M.-M. is to the of the Shc PTB domain to the overall entropy-driven of its high affinity binding to phosphopeptides. The PTB domains of IRS-1 and Shc show very sequence homology but a of pleckstrin homology domains (17Zhou M.-M. Ravichandran K.S. Olejniczak E.T. Petros A.P. Meadows R.P. Sattler M. Harlan J.E. Wade W. Burakoff S.J. Fesik S.W. Nature. 1995; 378: 584-592Crossref PubMed Scopus (324) Google Scholar, 18Zhou M.-M. B. Olejniczak E.T. Meadows R.P. M. Trüb T. Shoelson S.E. Fesik S.W. Biol. PubMed Scopus Google Scholar, S. Trüb T. R. Shoelson S.E. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar, Schlessinger J. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). The domains have to bind to of proteins and and are important for proteins that the domain to the surface Schlessinger J. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar, J.E. Fesik S.W. Nature. 1995; Scholar). we have recently that the PTB domain of Shc can bind to the tyrosine-phosphorylated proteins and receptors and to and events are for tyrosine phosphorylation of Shc following receptor activation K.S. M.-M. Harlan J.E. S. Fesik S.W. Burakoff S.J. Mol. Cell. Biol. PubMed Google Scholar). that proteins in other signaling molecules can protein-protein interactions in a These signaling proteins of and J. E. Margolis B. Mol. Cell. Biol. PubMed Scopus Google Scholar, Wiley S. Cantley L. J. Pawson T. S. A. PubMed Scopus Google Scholar, Lee M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). these results that this can for for protein-protein or interactions via distinct In we have in this that the two structurally but functionally distinct PTB domains of Shc and IRS-1 recognize the NPXpY phosphopeptides in a distinct from the analysis the of the interactions of the phosphopeptides with the Shc and IRS-1 PTB results support the that residues in and the NPXpY motif are in the of with the Shc and IRS-1 PTB the of the in the of these signaling in addition to play a in the of in signal transduction. W. Fesik for the of the PTB domains of Shc and are to and for on the isothermal titration Wolf for and E. for of the