title: Regions outside of conserved PxxPxR motifs drive the high affinity interaction of GRB2 with SH3 domain ligands.
abstract: SH3 domains are evolutionarily conserved protein interaction domains that control nearly all cellular processes in eukaryotes. The current model is that most SH3 domains bind discreet PxxPxR motifs with weak affinity and relatively low selectivity. However, the interactions of full-length SH3 domain-containing proteins with ligands are highly specific and have much stronger affinity. This suggests that regions outside of PxxPxR motifs drive these interactions. In this study, we observed that PxxPxR motifs were required for the binding of the adaptor protein GRB2 to short peptides from its ligand SOS1. Surprisingly, PxxPxR motifs from the proline rich region of SOS1 or CBL were neither necessary nor sufficient for the in vitro or in vivo interaction with full-length GRB2. Together, our findings show that regions outside of the consensus PxxPxR sites drive the high affinity association of GRB2 with SH3 domain ligands, suggesting that the binding mechanism for this and other SH3 domain interactions may be more complex than originally thought.
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, IA 52242, United States.
authors.forename: Rebekah R
authors.initials: RR
authors.lastname: Bartelt
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, IA 52242, United States.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Light
authors.affiliation: Program in Immunology, University of Iowa, Iowa City, IA 52242, United States.
authors.forename: Aldo
authors.initials: A
authors.lastname: Vacaflores
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, IA 52242, United States.
authors.forename: Alayna
authors.initials: A
authors.lastname: Butcher
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, IA 52242, United States.
authors.forename: Madhana
authors.initials: M
authors.lastname: Pandian
authors.affiliation: University of Chicago, Chicago, IL 60637, United States.
authors.forename: Piers
authors.initials: P
authors.lastname: Nash
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, IA 52242, United States; Program in Immunology, University of Iowa, Iowa City, IA 52242, United States. Electronic address: jon-houtman@uiowa.edu.
authors.forename: Jon C D
authors.initials: JC
authors.lastname: Houtman
mesh_terms: D020816:Amino Acid Motifs; D051380:GRB2 Adaptor Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D011485:Protein Binding / Q000502:physiology; D020837:SOS1 Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D020837:SOS1 Protein
keywords: CBL; GRB2; SH3 domains; SOS1; Signal transduction