Agonist binding to peptide hormone receptors

Abstract

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.

Investigation of mechanism of desmopressin binding in vasopressin V2 receptor versus vasopressin V1a and oxytocin receptors: Molecular dynamics simulation of the agonist‐bound state in the membrane–aqueous system

“…70 The molecular basis for the significance of these two residues has not been defined; however, it has been suggested that it could be involved in the intramolecular interactions with negatively charged residues. 69,70 Molecular modeling in this study may help to explain this mechanism. In the inactive state of V2R, the R32 side chain is exposed toward the extracellular side and forms a salt bridge with the conserved EL3 E303 (see Figure 5B).…”

“…The equivalent arginyl (R46 and R34 in V1aR and OTR, respectively) has been identified as playing a critical role in high-affinity agonist binding. 68,69 In addition, E 1.35 46 has been recently determined to be critical for AVP binding in V1aR. 70 The molecular basis for the significance of these two residues has not been defined; however, it has been suggested that it could be involved in the intramolecular interactions with negatively charged residues.…”

Role of extracellular domains in PBAN/pyrokinin GPCRs from insects using chimera receptors

“…The reason behind different levels of activation between QQ-PBANR and chimeric PBANR-CHN or PK1-CHN is unclear. It could be that N-glycosylation in the N-terminus of PBAN-R might not be directly involved in PBAN binding but plays a role in receptor stability or proper folding on the cell surface as shown in human GPCRs (Zhang et al, 2001;Wheatley et al, 2003).…”

An Influence of the Aromatic Side Chains Conformations in Positions 2 and 3 of Vasopressin Analogs on Interactions with Vasopressin and Oxytocin Receptors

“…Foremost, there are crucial interactions between the N-terminus of V 2 R and the ligand, where the most important is the interaction with the highly conserved R32. The equivalent arginyl (R46 and R34 in V 1a R and OTR, respectively) has been identified as playing a critical role in high affinity agonist binding [45,46]. Moreover, the molecular basis for the significance of this residue for dDAVP binding in V 2 R has been proposed in our earlier paper [38].…”