RT Journal Article SR Electronic T1 Crystal structure of human endothelin ETb receptor in complex with peptide inverse agonist IRL2500 JF bioRxiv FD Cold Spring Harbor Laboratory SP 460410 DO 10.1101/460410 A1 Chisae Nagiri A1 Wataru Shihoya A1 Asuka Inoue A1 Francois Marie Ngako Kadji A1 Junken Aoki A1 Osamu Nureki YR 2018 UL http://biorxiv.org/content/early/2018/11/02/460410.abstract AB Endothelin receptors (ET A and ET B) are G-protein coupled receptors activated by endothelin-1 and are involved in blood pressure regulation. IRL2500 is a peptide-mimetic of the C-terminal tripeptide of endothelin-1, and has been characterized as a potent ET B-selective antagonist, which has preventive effects against brain edema. Here, we report the crystal structure of the human ET B receptor in complex with IRL2500 at 2.7 A-resolution. The structure revealed the different binding modes between IRL2500 and ET-1, and provides structural insights into its ET B-selectivity. Notably, the biphenyl group of IRL2500 penetrates into the transmembrane core proximal to D2.50, stabilizing the inactive conformation. Using the newly-established constitutively active mutant, we clearly demonstrate that IRL2500 functions as an inverse agonist for the ET B receptor. The current findings will expand the chemical space of ETR antagonists and facilitate the design of inverse agonists for other class A GPCRs.