Mechanism of Folding and Binding of the N-Terminal SH2 Domain from SHP2

SHP2 is a phosphatase protein, involved in many cellular pathways, comprising two SH2 domains (namely N-SH2 and C-SH2) and a phosphatase domain. Among others, the interaction between SHP2 and Gab2 (Grb2 associated binder) is critical in cell death and differentiation. SHP2 binds to Gab2 through its SH2 domains, which recognize specific regions of Gab2 characterized by the presence of a phosphorylated tyrosine. In order to shed light on the dynamic and functional properties of this protein-protein interaction, we studied the mechanism of folding of N-SH2 and the binding process to a peptide mimicking a region of Gab2. The data presented represent the first description by stopped-flow of the kinetics of binding of an SH2 domain in solution. By performing experiments at different ionic strengths, we elucidate the electrostatic nature of the interaction, highlighting a key role of the negative charge of the phosphotyrosine in the recognition event of the reaction. Furthermore, by analyzing the equilibrium and kinetics of folding of N-SH2 folding we demonstrate the presence of an intermediate along the folding pathway. These results are discussed in the light of previous works on another SH2 domain.