Abstract
Growth factor receptor-bound 2 (Grb2) is an important link in the receptor tyrosine kinase signaling cascades. It is involved in crucial processes, both physiological (mainly embryogenesis) and pathological (different types of cancer). Several binding partners of all three domains (SH3–SH2–SH3) of this adaptor protein are well described, such as ErbB family members for the SH2 domain and Sos for the SH3 domains. How the different domains interact with each other, both structurally and functionally, is still unclear. These interactions could be essential for regulation processes, and therefore are of great interest. Although a lot of structural data on Grb2 exist, they describe either individual domains, ligand-bound conformations, or frozen pictures of the protein captured by crystallography. Here we report the assignment of backbone and of ^{13}hbox {C}_beta chemical shifts of full-length, apo-Grb2 in solution. In addition to the assigned conformation corresponding to three well-folded domains, a set of peaks compatible with the presence of an unfolded conformation of the N-terminal SH3 domain is observed. This assignment paves the way for future studies of inter-domain interactions and dynamics that have to be taken into account when studying the regulation of Grb2 interactions and signaling pathways.
Highlights
Growth factor receptor-bound 2 (Grb2) is an adaptor protein essential for early steps of embryogenesis, especially differentiation (Cheng et al 1998), but it was shown to be upregulated in a subset of breast cancers (Daly et al 1994)
It was originally discovered in humans as the missing link between receptor tyrosine kinases (RTKs) and the Ras/ MAPK pathway (Lowenstein et al 1992)
Grb2 is 217 residues long and is made up of three domains: a central SH2 domain, a well-described type of phosphotyrosine-binding domain, is flanked by two SH3 domains that bind to proline-rich motifs
Summary
The structures of the NSH3 domain in complex with Sos proline-rich peptides (PDB 1GBR) and of the CSH3 free domain (PDB 1GFC) were solved by NMR soon after Grb identification (Goudreau et al 1994; Wittekind et al 1994; Kohda et al 1994). The 3.1 Å resolution structure of full-length Grb was solved by X-ray crystallography (PDB 1GRI) (Maignan et al 1995). In this structure Grb is a dimer, but the oligomeric state of Grb in solution remains largely controversial, just like the presence and nature of inter-domain interactions. The behavior of apo-Grb in solution is still poorly defined, it is essential to decipher the interdependence of its domains and of their binding to different motifs
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