Identification of a constitutively active mutant of the human oxytocin receptor

Oxytocin (OT) and vasopressin (AVP) receptors belong to the G-protein-coupled receptor family; in these receptors, the peptide agonists bind to a region delimited by the upper third of the transmembrane part of the molecule (1) and the molecular interactions responsible for agonist selectivity have been extensively investigated (2–5). However, nothing is known on the intramolecular changes that characterize the active conformation(s) of these receptors. In order to get a better understanding of the process of receptor activation, we started a project aimed at the identification of the key residues involved in stabilizing the active conformation(s) of the human oxytocin receptor.