Abstract
SHP2 is a non-receptor protein tyrosine phosphatase involved in many cellular processes including growth, differentiation, and apoptosis. Regulation of SHP2 is mediated largely by controlling an intrinsic protein conformational equilibrium between closed, inactive and open, active states. While SHP2 activation is normally achieved by binding an allosteric ligand, mutagenic disruption of SHP2’s active/inactive equilibrium has been shown to result in numerous cancers and developmental pathologies. While the closed form of SHP2 is well understood, the process of activation remains obscure. Therefore, I aimed to visualize the open, active structure, along with its mechanism of activation in the presence and absence of an allosteric activator. Using a combination of X-ray crystallography, enzyme turnover experiments, and lanthanide-enhanced NMR spectroscopy, I found the regulatory domains sample two states within the open conformation, each specialized to either inactivate or activate SHP2. To buttress my findings, I obtained residual dipolar couplings of the SHP2 regulatory domains, which independently probed the conformational space sampled.\r Additionally, I studied the binding of SHP2 to a natural allosteric activator, bisphosphorylated IRS-1, to better understand the structural dynamics behind SHP2’s allosteric activation. Coupling enzymatic assays and NMR spectroscopy, I found the doubly phosphorylated tail of IRS-1 tightly binds and activates SHP2. Investigation at the atomic level through NMR revealed IRS-1 binding to SHP2’s regulatory domains induces a global conformational switch. Conclusively, IRS-1 binding promotes a global conformational change in SHP2 leading to a single, open structure.