Cryo-EM structure of cell-free synthesized human histamine H₂receptor coupled to heterotrimeric G_sprotein in lipid nanodisc environment

Abstract

Here we describe the cryo-electron microscopy structure of the human histamine 2 receptor (H2R) in an active conformation with bound histamine and in complex with Gs heterotrimeric protein at an overall resolution of 3.4 angstroem. The complex was generated by cotranslational insertion into preformed nanodisc membranes using cell-free synthesis in E. coli lysates. It is the first structure obtained by this detergent-free strategy and the first GPCR/Gs complex structure in lipid environment. Structural comparison with the inactive conformation of H2R and the inactive and Gq-coupled active state of H1R together with structure-guided functional experiments reveal molecular insights into the specificity of ligand binding and G protein coupling for this receptor family. We demonstrate lipid-modulated folding of cell-free synthesized H2R, its agonist-dependent internalization and its interaction with endogenously synthesized H1R and H2R in HEK293 cells by applying a recently developed nanotransfer technique.