Comparison of the orientation and conformations of Gq mimetic proteins in class A GPCRs.

Each of the available Gq (Gq mimetic chimera) bound structures is displayed relative to the structure of the CCK1R–mGsqi complex. (A) CCK1R–mGsqi and 5HT_2AR-mGsqi (PDB:6WHA). (B) CCK1R–mGsqi and OX₂R-mGsqi (PDB:7L1U). (C) CCK1R–mGsqi and M₁ mAChR-G11/i chimera [PDB:6OIJ). The structures are aligned to the CCK1R. The protein backbone is shown in ribbon format coloured according to the displayed legends. The carboxyl-terminal residues of the G protein αH5 are shown in stick representation coloured by heteroatom. All receptors have a similar, narrow, intracellular G protein binding cavity with only small differences in the angle or translational position of the αH5 when bound to the receptor (A–C), with greatest difference seen between CCK1R and M₁ mAChR complexes (C). αH5, α5 helix; CCK, cholecystokinin; CCK1R, cholecystokinin type 1 receptor; GPCR, G protein–coupled receptor.

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