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. 2019 Nov;96(5):527–541. doi: 10.1124/mol.118.115113

Fig. 4.

Fig. 4.

Transmembrane allosteric sites in GPCRs span the entire bilayer normal (z-axis). X-ray structures (PDB IDs are given in the brackets) of class A and class B GPCRs and their ligands bound to transmembrane allosteric sites embedded within and facing the lipid bilayer. The receptors and bound ligands are present in secondary structure (gray) and stick (blue) representations, respectively. CRF1R, corticotropin-releasing factor receptor 1; GCGR, glucagon receptor; GLP-1, glucagon-like peptide-1 receptor; GPR40, free fatty acid receptor; P2Y1, P2Y purinoreceptor 1; PAR2, protease activated receptor 2. The approximate positions of the upper and lower leaflets of a hypothetical lipid bilayer are marked by two horizontal lines perpendicular to the bilayer normal. The Ballesteros and Weinstein amino acid numbering system (Ballesteros and Weinstein, 1995) used in the main text as a superscript of the absolute sequence number, begins with the TMH number and is followed by a locant (0.50 assigned to most highly conserved amino acid in a TMH and other residues numbered relative to it).