Crystal Structure of the PAC1R Extracellular Domain Unifies a Consensus Fold for Hormone Recognition by Class B G-Protein Coupled Receptors
Figure 3
Superimposition of the backbone of the ECD of class B members.
(a) Superimposition of the backbone of the ECD of class B members GIP1R (black, PDB code:2QKH), GLP1R (red, PDB code:3C5T), PAC1R (green, PDB code:3N94) and VIP2R (blue, PDB code:2X57). The disulphide bridges C34–C63, C54–C97 and C77–C113 are labelled. (b) superimposition of conserved residues. The color scheme is as in panel A. (c) Ligand orientation in class B GPCRs. The ligands incretin of GIP1R, glucagon of GLP1R and PTH of PTH1R are shown in black, orangeand yellow, respectively. For simplicity the surface diagram of PAC1R ECD alone is shown in white with the trace of PAC1R in green. PACAP from the NMR structure is shown in magenta. While all the class B ligands follow the same binding site and orientation, PACAP of the NMR structure is shown to bind PAC1R at a different location. Furthermore, its polarity does not follow that of the other ligands.