Solution structure and mutational analysis of pituitary adenylate cyclase-activating polypeptide binding to the extracellular domain of PAC1-R^sub S

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 19; p. 7875
• Main Authors: Sun, Chaohong, Song, Danying, Davis-Taber, Rachel A, Barrett, Leo W
• Format: Journal Article
• Language: English
• Published: Washington National Academy of Sciences 08.05.2007
• Subjects: Binding sites; Biochemistry; Mutation; Peptides; Pituitary gland; Proteins
• ISSN: 0027-8424; 1091-6490

The pituitary adenylate cyclase-activating polypeptide (PACAP) receptor is a class TI U protein-coupled receptor that contributes to many different cellular functions including neurotransmission, neuronal survival, and synaptic plasticity. The solution structure of the potent antagonist PACAP (residues 6'-38') complexed to the N-terminal extracellular (EC) domain of the human splice variant hPAC1-R-short (hPAC1-R...) was determined by NMR. The PACAP peptide adopts a helical conformation when bound to hPAC1-R... with a bend at residue A18' and makes extensive hydrophobic and electrostatic interactions along the exposed β-sheet and interconnecting loops of the N-terminal EC domain. Mutagenesis data on both the peptide and the receptor delineate the critical interactions between the C terminus of the peptide and the C terminus of the EC domain that define the high affinity and specificity of hormone binding to hPAC1-Rs. These results present a structural basis for hPAC1-R... selectivity for PACAP versus the vasoactive intestinal peptide and also differentiate PACAP residues involved in binding to the N-terminal extracellular domain versus other parts of the full-length hPAC1-R... receptor. The structural, mutational, and binding data are consistent with a model for peptide binding in which the C terminus of the peptide hormone interacts almost exclusively with the N-terminal EC domain, whereas the central region makes contacts to both the N-terminal and other extracellular parts of the receptor, ultimately positioning the N terminus of the peptide to contact the transmembrane region and result in receptor activation. (ProQuest-CSA LLC: ... denotes formulae/symbols omitted.)