Cryo-EM structure of the adenosine A 2A receptor coupled to an engineered heterotrimeric G protein

Elife. 2018 May 4;7:e35946. doi: 10.7554/eLife.35946.

Abstract

The adenosine A2A receptor (A2AR) is a prototypical G protein-coupled receptor (GPCR) that couples to the heterotrimeric G protein GS. Here, we determine the structure by electron cryo-microscopy (cryo-EM) of A2AR at pH 7.5 bound to the small molecule agonist NECA and coupled to an engineered heterotrimeric G protein, which contains mini-GS, the βγ subunits and nanobody Nb35. Most regions of the complex have a resolution of ~3.8 Å or better. Comparison with the 3.4 Å resolution crystal structure shows that the receptor and mini-GS are virtually identical and that the density of the side chains and ligand are of comparable quality. However, the cryo-EM density map also indicates regions that are flexible in comparison to the crystal structures, which unexpectedly includes regions in the ligand binding pocket. In addition, an interaction between intracellular loop 1 of the receptor and the β subunit of the G protein was observed.

Keywords: G protein-coupled receptor; GPCR; adenosine receptors; biochemistry; chemical biology; mini-G protein; molecular biophysics; none; structural biology; structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine-5'-(N-ethylcarboxamide) / metabolism
  • Cryoelectron Microscopy
  • Heterotrimeric GTP-Binding Proteins / chemistry
  • Heterotrimeric GTP-Binding Proteins / metabolism*
  • Heterotrimeric GTP-Binding Proteins / ultrastructure*
  • Humans
  • Hydrogen-Ion Concentration
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Receptor, Adenosine A2A / chemistry
  • Receptor, Adenosine A2A / metabolism*
  • Receptor, Adenosine A2A / ultrastructure*

Substances

  • Receptor, Adenosine A2A
  • Adenosine-5'-(N-ethylcarboxamide)
  • Heterotrimeric GTP-Binding Proteins