The structure sketch map of PAC1 (A, B).

The HSDCIF motif is indicated as red. The homology analysis between PACAP and PAC1-EC1 (C). The red region showed the HSDCIF motif and its high homologue PACAP (1–6). The construction of D-PAC1 (D). The gene coding D-PAC1 with the deletion of the HSDCIF motif was amplified using over-lap PCR (The arrows represented the primers used to amplify the genes coding D-PAC1 and PAC1.).