Cryo-EM structure of cell-free synthesized human histamine H2 receptor coupled to heterotrimeric Gs protein in lipid nanodisc environment

Abstract Here we describe the cryo-electron microscopy structure of the human histamine 2 receptor (H 2 R) in an active conformation with bound histamine and in complex with G s heterotrimeric protein at an overall resolution of 3.4 Å. 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/G s complex structure in lipid environment. Structural comparison with the inactive conformation of H 2 R and the inactive and G q -coupled active state of H 1 R 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 H 2 R, its agonist-dependent internalization and its interaction with endogenously synthesized H 1 R and H 2 R in HEK293 cells by applying a recently developed nanotransfer technique.