Figure 5. Structural impact of the T42A mutation on phosphotyrosine and proximal sequence recognition.

(A) Hydrogen bonding of Thr⁴² in SHP2 N-SH2^WT to the phosphoryl group of phosphopeptide ligands in several crystal structures (PDB: 6ROY, 1AYA, 1AYB, 3TL0, 5DF6, 5X94, and 5X7B). (B) Representative structures of (B) N-SH2^WT and (C) N-SH2^T42A bound to the PD-1 pTyr²²³ (ITIM) peptide at the ends of respective trajectories. (D) Overlay of the states shown in panels B and C. The N-SH2^WT state is in yellow with a dark-gray ligand. The N-SH2^T42A state is in light gray, with a light gray ligand. (E) Distribution of distances between the Lys⁵⁵ Nζ atom and the phosphotyrosine phosphorus atοm in simulations of the PD-1 pTyr²²³ peptide bound to N-SH2^WT (black) or N-SH2^T42A (red). (F) Distribution of distances between the Lys⁵⁵ Nζ atom and the +2 Glu Cδ atom in simulations of the PD-1 pTyr²²³ peptide bound to N-SH2^WT (black) or N-SH2^T42A (red). (G) An ion pair between Lys⁵⁵ and the +2 Glu residue (Glu 225) in the PD-1 pTyr²²³ (ITIM) peptide, frequently observed in N-SH2^T42A simulations. (H) Peptide-specific effects of the T42A mutation in the presence and absence of the K55R mutation. N = 3–5 independent titrations. All fold-changes and respective p-values can be found in Table S2.