title: Unusual binding of Grb2 protein to a bivalent polyproline-ligand immobilized on a SPR sensor: intermolecular bivalent binding.
abstract: The Grb2 adapter protein is involved in the activation of the Ras signaling pathway. It recruits the Sos protein by binding of its two SH3 domains to Sos polyproline sequences. We observed that the binding of Grb2 to a bivalent ligand, containing two Sos-derived polyproline-sequences immobilized on a SPR sensor, shows unusual kinetic behavior. SPR-kinetic analysis and supporting data from other techniques show major contributions of an intermolecular bivalent binding mode. Each of the two Grb2 SH3 domains binds to one polyproline-sequence of two different ligand molecules, facilitating binding of a second Grb2 molecule to the two remaining free polyproline binding sites. A molecular model based on the X-ray structure of the Grb2 dimer shows that Grb2 is flexible enough to allow this binding mode. The results fit with a role of Grb2 in protein aggregation, achieving specificity by multivalent interactions, despite the relatively low affinity of single SH3 interactions.
authors.affiliation: Department of Medicinal Chemistry & Chemical Biology, Utrecht Institute of Pharmaceutical Sciences, Universiteitsweg 99, 3484 CG Utrecht, The Netherlands. N.J.deMol@uu.nl
authors.forename: Nico J
authors.initials: NJ
authors.lastname: de Mol
authors.forename: John A W
authors.initials: JA
authors.lastname: Kruijtzer
authors.forename: Ed E
authors.initials: EE
authors.lastname: Moret
authors.forename: Isabelle
authors.initials: I
authors.lastname: Broutin
authors.forename: Rob M J
authors.initials: RM
authors.lastname: Liskamp
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D051380:GRB2 Adaptor Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D015398:Signal Transduction / Q000502:physiology; D018909:src Homology Domains
chemical_list: D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D010455:Peptides; C011083:polyproline