Agonist binding to peptide hormone receptors.
A fundamental issue in molecular pharmacology is to define how agonist-receptor interaction differs from that of antagonist-receptor interaction. The V(1a) vasopressin receptor (V(1a)R) is a member of a family of related G-protein-coupled receptors (GPCRs) that are activated by vasopressin, oxytocin (OT) and related peptides. A segment of the N-terminus that was required for agonist binding, but not antagonist binding, was identified by characterizing truncated V(1a)R constructs. Site-directed mutagenesis revealed that a single residue (Arg(46)) was critical for agonist binding and receptor activation. The N-terminus of the related OT receptor (OTR) could recover agonist binding in a chimaeric OTR(N)-V(1a)R construct. Furthermore, Arg(34) of the human OTR, which corresponds to Arg(46) of the rat V(1a)R, provided agonist-specific binding epitopes in the OTR, indicating a conserved function of this locus throughout this GPCR subfamily. Mutation of Arg(46) revealed that high-affinity agonist binding had an absolute requirement for arginine at this position.
Wheatley
M
M
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. m.wheatley@bham.ac.uk
Hawtin
S R
SR
Wesley
V J
VJ
Howard
H C
HC
Simms
J
J
Miles
A
A
McEwan
K
K
Parslow
R A
RA
D000818:Animals; D001120:Arginine / Q000737:chemistry; D001665:Binding Sites; D000939:Epitopes; D006801:Humans; D008024:Ligands; D008051:Lipid Bilayers; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018000:Receptors, Peptide / Q000819:agonists* / Q000378:metabolism*; D017483:Receptors, Vasopressin / Q000378:metabolism
D000939:Epitopes; D008024:Ligands; D008051:Lipid Bilayers; D018000:Receptors, Peptide; D017483:Receptors, Vasopressin; D001120:Arginine