Identification by photoaffinity labeling of the extracellular N-terminal domain of PAC1 receptor as the major binding site for PACAP

►Physical sites of interaction between PAC1 receptor (PAC1-R) and PACAP are defined. ►Extracellular N-terminal domain of PAC1-R is the major binding site of PACAP. ►N-terminus of PACAP attaches to the Ser98 - Met111 segment of PAC1-R. ►Amino acid at position 6 of PACAP labels the Ser124 - Glu125 dipeptide of PAC1-R. ►Residue 22 of PACAP has a contact point in the Ser141 - Met172 segment of PAC1-R.