Fig. 4.

E78^2.50-mediated interhelical hydrogen-bond network in the transmembrane core. a Amino acid sequence alignment of residues involved in the allosteric sodium ion-binding site in NK₁R and other class A GPCRs (Ballesteros-Weinstein numbers indicated). b, c Extracellular view on the hydrogen-bonding network in the transmembrane core of netupitant-bound NK₁R (b) and the dopamine D4 receptor (D₄R, PDB ID 5WIV) (c). The receptor backbone is shown in ribbon representations coloured blue and yellow, respectively. Ordered waters are shown as red spheres and hydrogen bonds are indicated by dashed blue lines. The sodium ion coordinated between D^2.50 and S^3.39 in the D₄R is shown as a purple sphere