Crystal Structure of the PAC1R Extracellular Domain Unifies a Consensus Fold for Hormone Recognition by Class B G-Protein Coupled Receptors
Figure 5
PAC1R and PACAP interaction model.
(a) (i) The surface charge distribution of PAC1R is depicted with red and blue potentials, ranging from −10 KeT to +10 KeT. The potentials were calculated using APBS [47]. PACAP is shown in cyan. Our docking result correlates well with other published class B GPCR ECD:ligand complex structures. (ii) The polarity of the N-terminal α-helix of PAC1R and the PACAP is in the same direction. Following other structures, PACAP residues 1–8 are not expected to make any contact with the ECD of PAC1R and hence not included in our docking study. (b) A close-up view of the interaction. The residues that are likely to make important contacts are shown as sticks and are labeled. K20′ and E104 form a salt bridge with a distance of 2.6 Å. (c) (i) Alphascreen of mutations in PAC1R affecting the binding to PACAP. All the mutations were made on the outer surface of the receptor so that the structural core of PAC1R is unaffected. The mutants and the wildtype receptor ECDs were assayed for interaction with biotin-PACAP(6–38) at increasing equimolar concentration to enable the reading of the assay to reach saturation. (ii) The location of the mutated residues on the surface of PAC1R ECD. ECD is coloured in green while the side chains of the mutated residues are shown as blue sticks.