Yj. Cao et al., THE AMINO-TERMINAL FRAGMENT OF THE ADENYLATE-CYCLASE ACTIVATING POLYPEPTIDE (PACAP) RECEPTOR FUNCTIONS AS A HIGH-AFFINITY PACAP FINDING DOMAIN, Biochemical and biophysical research communications, 212(2), 1995, pp. 673-680
The PACAP receptor represents a member of a novel subfamily of G-prote
in coupled receptors with a common structurally conserved extracellula
r domain of about 150 amino acids. We have addressed the question whet
her this extracellular amino-terminus of the PACAP type I receptor can
solely function as a PACAP binding domain. For that purpose a cDNA wa
s constructed that encodes the membrane-anchored amino-terminus of the
rat PACAP receptor including the decapeptide epitope EQKLISEEDL for i
mmunodetection. COS-7 cells were transfected with this cDNA and a comp
arable construct of the wild-type receptor. Binding analysis showed th
at the amino-terminal fragment of the PACAP receptor bound PACAP with
high-affinity (K-d=3.8 nM; B-max=12.8 pmol/mg protein). In comparison
to the full-length receptor (K-d=0.2 nM; B-max=1.96 pmol/mg protein) i
ts affinity was reduced by a factor of about 20. The results suggest t
hat the amino-terminus of the PACAP receptor functions as the major bi
nding site for its ligand. (C) 1995 Academic Press, Inc.