Agonist-specific, high-affinity binding epitopes are contributed by an arginine in the N-terminus of the human oxytocin receptor

Victoria J. Wesley, Stuart R. Hawtin, Helen C. Howard, Mark Wheatley

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

The effects of the peptide hormone oxytocin (OT) are mediated by the oxytocin receptor, which is a member of the G-protein-coupled receptor family. Defining differences between the binding of agonists and antagonists to the OTR, at the molecular level, is of fundamental importance to understanding OTR activation and to rational drug design. Previous reports have indicated that the N-terminus of the OTR is required for OT binding. The aim of this study was to identify which individual residues within the N-terminal domain of the human OTR provided these OT binding epitopes. A series of truncated OTRs and mutant receptor constructs with systematic alanine substitution were characterized with respect to their pharmacological profile and intracellular signaling capability. Although a number of residues within the OTR will be required for optimal OT-OTR interaction, our data establish that Arg34 within the N-terminal domain contributes to high-affinity OT binding. Removal of Arg34 by truncation or substitution resulted in a 2000-fold decrease in OT affinity. In addition, we show that the arginyl at this locus is required for high-affinity binding of agonists in general. However, the importance of Arg34 is restricted to agonist interaction with the OTR, as it was not required for binding peptide antagonist or non-peptide antagonist. It is noteworthy that the corresponding Arg in the related rat V1a vasopressin receptor is also required for high-affinity agonist binding. This study defines, at the molecular level, the role of the N-terminus of the OTR in high-affinity agonist binding and identifies a key residue for this function.

Original languageEnglish
Pages (from-to)5086-5092
Number of pages7
JournalBiochemistry
Volume41
Issue number16
DOIs
Publication statusPublished - 27 Mar 2002
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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