Fig. 4: Molecular determinants and structural basis for the selective binding of RS79948 to α_2CAR over α_1BAR.

a Affinity of RS79948 for α_1BAR, α_2CAR, and chimeric α_1BAR-α_2C mutants. Single amino acid substitutions in α_1BAR are indicated in the construct names and correspond to the α_2CAR sequence at either one of positions 3.28, 3.29, 45.52, or 6.55. The α_1BAR-α_2C(YLLY) chimera corresponds to the quadruple mutant. Data are shown as mean values ± standard error of the mean (SEM) of 3–6 independent experiments performed in triplicate. The underlying data points are depicted as black diamonds, and the exact n, SEM, and 95% confidence interval of the mean are reported in Supplementary Table 6. Differences in affinities were evaluated by a statistical test as detailed in Supplementary Table 7. b Structural role of Y127^3.28, L128^3.29, L204^45.52, and Y402^6.55 in the binding of RS79948 to α_2CAR (PDB ID: 6KUW²⁶). TM1, ECL3, and TM7 have been omitted for clarity. Receptor residues are shown as van der Waals spheres and as sticks, except for D131^3.32, which is shown as sticks only; RS79948 is shown as sticks. Oxygen, nitrogen, and sulfur atoms are depicted in red, blue, and yellow, respectively. c Superposition of α_1BAR_XTAL bound to (+)-cyclazosin and α_2CAR-RS79948 (PDB ID: 6KUW²⁶), focusing on the residues outlined in panel b. (+)-Cyclazosin, TM1, TM2, ECL1, ECL3, and TM7, have been omitted for clarity. Receptor residues and RS79948 are shown as sticks. V197 is shown to Cβ only because its side chain is not resolved in the electron density map. Source data are provided as a Source Data file.