Phosphatase SHP2 pathogenic mutations enhance activity by altering conformational sampling.

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• SH2 domains mediate cellular signaling by binding phosphopeptide ligands.
• The protein tyrosine phosphatase SHP2 is a key regulator of cellular signaling, and its dysregulation is implicated in disease.
• Pathogenic mutations in SHP2 often occur near the PTP/N-SH2 interface, but mechanisms for mutations in regulatory SH2 domains are less understood.

Purpose of the Study:

• To investigate the atomic mechanisms of SHP2 regulation and dysregulation.
• To elucidate the controversial mechanism of the T42A mutation in the N-SH2 domain, which paradoxically increases phosphopeptide binding affinity.
• To reconcile conflicting models of SHP2 activation by phosphopeptide binding.

Main Methods:

• X-ray ensemble refinement
• NMR relaxation studies
• Computational modeling of conformational ensembles

Main Results:

• The T42A mutation shifts the conformational ensemble of peptide-bound N-SH2 toward a stabilized zipped β-sheet state.
• This mutation suppresses millisecond conformational exchange, indicating enhanced stability of the zipped conformation.
• The conformational shift provides a structural basis for the increased binding affinity observed in the T42A mutant.

Conclusions:

• The T42A mutation hyperactivates SHP2 by stabilizing a functionally relevant conformation.
• Complementary structural and dynamic approaches reveal critical regulatory mechanisms in SHP2.
• Findings may inform broader principles of SH2 domain-mediated phosphopeptide recognition.