In:
European Journal of Biochemistry, Wiley, Vol. 267, No. 13 ( 2000-07), p. 4253-4263
Abstract:
Despite their opposite effects on signal transduction, the nonapeptide hormone arginine‐vasopressin (AVP) and its V 1a receptor‐selective cyclic peptide antagonist d(CH 2 ) 5 [Tyr(Me)2]AVP display homologous primary structures, differing only at residues 1 and 2. These structural similarities led us to hypothesize that both ligands could interact with the same binding pocket in the V 1a receptor. To determine receptor residues responsible for discriminating binding of agonist and antagonist ligands, we performed site‐directed mutagenesis of conserved aromatic and hydrophilic residues as well as nonconserved residues, all located in the transmembrane binding pocket of the V 1a receptor. Mutation of aromatic residues of transmembrane region VI (W304, F307, F308) reduced affinity for the d(CH 2 ) 5 [Tyr(Me)2]AVP and markedly decreased affinity for the unrelated strongly hydrophobic V 1a ‐selective nonpeptide antagonist SR 49059. Replacement of these aromatic residues had no effect on AVP binding, but increased AVP‐induced coupling efficacy of the receptor for its G protein. Mutating hydrophilic residues Q108, K128 and Q185 in transmembrane regions II, III and IV, respectively, led to a decrease in affinity for both agonists and antagonists. Finally, the nonconserved residues T333 and A334 in transmembrane region VII, controlled the V 1a /V 2 binding selectivity for both nonpeptide and cyclic peptide antagonists. Thus, because conserved aromatic residues of the V 1a receptor binding pocket seem essential for antagonists and do not contribute at all to the binding of agonists, we propose that these residues differentiate agonist vs. antagonist ligand binding.
Type of Medium:
Online Resource
ISSN:
0014-2956
,
1432-1033
DOI:
10.1046/j.1432-1033.2000.01472.x
Language:
English
Publisher:
Wiley
Publication Date:
2000
detail.hit.zdb_id:
1398347-7
detail.hit.zdb_id:
2172518-4
SSG:
12
Permalink