Cryo-EM structure of an activated GPCR-G protein complex in lipid nanodiscs.

Miao Gui,Zi-Fu Wang,Andreas Plückthun,Hao Wu,Lisa Merklinger,Lena Morstein,Christoph Gorgulla,James J Yu,Christoph Klenk,Mahmoud L Nasr,Franz Hagn,Zhen-Yu J Sun,Meng Zhang,Gerhard Wagner,Alan Brown

doi:10.1038/s41594-020-00554-6

Abstract

G-protein-coupled receptors (GPCRs) are the largest superfamily of transmembrane proteins and the targets of over 30% of currently marketed pharmaceuticals. Although several structures have been solved for GPCR-G protein complexes, few are in a lipid membrane environment. Here, we report cryo-EM structures of complexes of neurotensin, neurotensin receptor 1 and Gαi1β1γ1 in two conformational states, resolved to resolutions of 4.1 and 4.2 Å. The structures, determined in a lipid bilayer without any stabilizing antibodies or nanobodies, reveal an extended network of protein-protein interactions at the GPCR-G protein interface as compared to structures obtained in detergent micelles. The findings show that the lipid membrane modulates the structure and dynamics of complex formation and provide a molecular explanation for the stronger interaction between GPCRs and G proteins in lipid bilayers. We propose an allosteric mechanism for GDP release, providing new insights into the activation of G proteins for downstream signaling.

Highlights

Several structures have been solved for Gprotein coupled receptors (GPCRs)-G protein complexes, few are in a lipid membrane environment
Lipid bilayers enhance the efficiency of NTS-neurotensin receptor 1 (NTSR1)-Gαi1β1γ1 complex formation
The purified NTS-NTSR1 complex was incorporated into 9-nm diameter covalently circularized nanodiscs, containing a mixture of zwitterionic lipid POPC and negatively charged lipid POPG, and belted by circularized membrane scaffold protein cNW9 (Fig. 1a and Extended Data Fig. 1)

Summary

Introduction

G-protein-coupled receptors (GPCRs) are the largest superfamily of transmembrane proteins and the targets of over 30% of currently marketed pharmaceuticals. The structures, determined in a lipid bilayer without any stabilizing antibodies or nanobodies, reveal an extended network of protein–protein interactions at the GPCR–G protein interface as compared to structures obtained in detergent micelles. We report cryo-EM structures of lipid bilayer-bound complexes of neurotensin, neurotensin receptor 1, and Gαi1β1γ1 protein in two conformational states, resolved to 4.1 and 4.2 Å resolution. The structures were determined in a lipid bilayer without any stabilizing antibodies/nanobodies, and provide a native-like platform for understanding the structural basis of GPCR-G protein complex formation.

Methods

Results

Conclusion