Fig. 2.

Energetic fingerprint of STX recognition by RcSxph. (A) ΔΔG comparisons for the indicated RcSxph STX binding pocket mutants relative to wild-type RcSxph. Colors indicate ΔΔG < −1 kcal⋅mol⁻¹ (blue), −1 ≤ ΔΔG ≤ 0 kcal⋅mol⁻¹ (light blue), 0 ≥ ΔΔG ≥ 1 kcal⋅mol⁻¹ (yellow), 1 ≥ ΔΔG ≥ 2 kcal⋅mol⁻¹ (orange), 2 ≥ ΔΔG ≥ 3 kcal⋅mol⁻¹ (red orange), and ΔΔG ≥ 3 (red). (B) Energetic map of alanine scan mutations on STX binding to the RcSxph STX binding pocket (PDB ID:6O0F) (10). Second-shell sites are in italics. Colors are as in A. (C and D) Structural interactions of STX with (C) RcSxph (PDB ID:6O0F) (10) and (D) human Na_V1.7 (PDB ID:6J8G) (40). Residues that are energetically important for the STX interaction are shown in space filling. Na_V1.7 selectivity filter “DEKA” ring residues are shown (white). Italics indicate corresponding residue numbers for rat Na_V1.4 (18).