Structure of endothelin ET[B] receptor–G[i] complex in a conformation stabilized by unique NPxxL motif

Abstract

Endothelin type B receptor (ET[B]R) plays a crucial role in regulating blood pressure and humoral homeostasis, making it an important therapeutic target for related diseases. ET[B]R activation by the endogenous peptide hormones endothelin (ET)−1–3 stimulates several signaling pathways, including G[s], G[i/o], G[q]/₁₁, G₁₂/₁₃, and β-arrestin. Although the conserved NPxxY motif in transmembrane helix 7 (TM7) is important during GPCR activation, ET[B]R possesses the lesser known NPxxL motif. In this study, we present the cryo-EM structure of the ET[B]R–G[i] complex, complemented by MD simulations and functional studies. These investigations reveal an unusual movement of TM7 to the intracellular side during ET[B]R activation and the essential roles of the diverse NPxxL motif in stabilizing the active conformation of ET[B]R and organizing the assembly of the binding pocket for the α5 helix of Gi protein. These findings enhance our understanding of the interactions between GPCRs and G proteins, thereby advancing the development of therapeutic strategies.