title: High affinity Grb2-SH3 domain ligand incorporating Cbeta-substituted prolines in a Sos-derived decapeptide.
abstract: Peptide ligands that disrupt MAPK pathways are of great interest for a better understanding of these signalling cascades and represent therefore an attractive target to control cell degenerative processes. In that context, selective disruption of the upstream Grb2/Sos complex in the Ras/MAPK cascade has focused extensive work. The Sos PPII decapeptide, which interacts with the Grb2-SH3 domains, has been modified in various positions and the best inhibitors designed so far are either dimeric ligands or peptoid analogues of the VPPPVPPRRR sequence. We report the synthesis of new Grb2 ligands in which the key Val5 residue has been replaced by a cis C(beta)-substituted proline. Both fluorescence and ITC assays have been employed to measure the affinity of these substituted peptides for a recombinant Grb2 protein. Whereas proline in position 5 completely abolished the binding potency, a cis C(beta)-methyl-L-proline restored the affinity. Other cis C(beta)-proline substituents led to a complete loss of binding potency. Combining the best modifications: a cis C(beta)-methylproline 5, N-acetylation, C-carboxamide and dimerization yielded a 560-fold affinity enhancement compared to the wild-type VPPPVPPRRR sequence. This study shows that C(beta)-substituted prolines may constitute a new alternative for PPII ligands, combining entropy and enthalpy beneficial effects.
authors.affiliation: Université Pierre et Marie Curie-Paris 6, UMR 7613, Paris, France; CNRS, UMR 7613, Synthèse, Structure et Fonction de Molécules Bioactives, Paris, France. jacquot@ccr.jussieu.fr
authors.forename: Yves
authors.initials: Y
authors.lastname: Jacquot
authors.forename: Isabelle
authors.initials: I
authors.lastname: Broutin
authors.forename: Emeric
authors.initials: E
authors.lastname: Miclet
authors.forename: Magali
authors.initials: M
authors.lastname: Nicaise
authors.forename: Olivier
authors.initials: O
authors.lastname: Lequin
authors.forename: Nicole
authors.initials: N
authors.lastname: Goasdoué
authors.forename: Charlotte
authors.initials: C
authors.lastname: Joss
authors.forename: Philippe
authors.initials: P
authors.lastname: Karoyan
authors.forename: Michel
authors.initials: M
authors.lastname: Desmadril
authors.forename: Arnaud
authors.initials: A
authors.lastname: Ducruix
authors.forename: Solange
authors.initials: S
authors.lastname: Lavielle
mesh_terms: D051380:GRB2 Adaptor Protein / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D011392:Proline / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D020664:Son of Sevenless Proteins / Q000737:chemistry* / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D051380:GRB2 Adaptor Protein; D008024:Ligands; D010446:Peptide Fragments; D020664:Son of Sevenless Proteins; D011392:Proline