Fig. 3: Structure basis of antagonist selectivity in ET_A and ET_B.

a The sulfonylamide in macitentan and zibotentan, along with the carboxylic acid group in ambrisentan, engage with the positively charged area (blue surface) in ET_A’s orthosteric pocket. b Three antagonists hinder the inward movement of W319^6.48’s side chain through analogous functional groups at the similar positions. c The conformation of F161^3.28 in different states. d In ET_B’s corresponding position, V177^3.28, offers a larger antagonist-binding pocket. e Different spatial accommodation of antagonists in ET_A and ET_B. The bulky hydrophobic group (4-t-butylphenyl) of bosentan is better adapted to ET_B, whereas the smaller hydrophobic group of macitentan shows a preference for ET_A. f Effects of V177^3.28F in ET_B on the antagonistic activities of ambrisentan and macitentan (n = 3). g Difference in pIC₅₀ values between ET_A and ET_B variants and WT in antagonist experiments. Data are presented as means ± SEM (n ≥ 3). All data were analyzed by one-way ANOVA by Dunnett’s multiple test compared with WT. For mutants, *P < 0.05, **P < 0.01, ***P < 0.001 and ****P < 0.0001 were considered statistically significant.