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

Nat Struct Mol Biol. 2021 Mar;28(3):258-267. doi: 10.1038/s41594-020-00554-6. Epub 2021 Feb 25.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allosteric Regulation
  • Cryoelectron Microscopy*
  • GTP-Binding Protein alpha Subunits, Gi-Go / chemistry
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism
  • GTP-Binding Protein alpha Subunits, Gi-Go / ultrastructure
  • GTP-Binding Protein beta Subunits / chemistry
  • GTP-Binding Protein beta Subunits / metabolism
  • GTP-Binding Protein beta Subunits / ultrastructure
  • GTP-Binding Protein gamma Subunits / chemistry
  • GTP-Binding Protein gamma Subunits / metabolism
  • GTP-Binding Protein gamma Subunits / ultrastructure
  • Guanosine Diphosphate / metabolism
  • Heterotrimeric GTP-Binding Proteins / chemistry
  • Heterotrimeric GTP-Binding Proteins / metabolism*
  • Heterotrimeric GTP-Binding Proteins / ultrastructure*
  • Humans
  • Lipid Bilayers* / chemistry
  • Lipid Bilayers* / metabolism
  • Micelles
  • Models, Molecular
  • Nanostructures / chemistry*
  • Neurotensin / chemistry
  • Neurotensin / metabolism
  • Protein Conformation
  • Receptors, Neurotensin / chemistry
  • Receptors, Neurotensin / metabolism*
  • Receptors, Neurotensin / ultrastructure*
  • Signal Transduction

Substances

  • GTP-Binding Protein beta Subunits
  • GTP-Binding Protein gamma Subunits
  • Lipid Bilayers
  • Micelles
  • Receptors, Neurotensin
  • neurotensin type 1 receptor
  • Guanosine Diphosphate
  • Neurotensin
  • GTP-Binding Protein alpha Subunits, Gi-Go
  • Heterotrimeric GTP-Binding Proteins