Modelling the peptide receptor interaction: selectivity of the oxytocin receptor

In this study the interactions of oxytocin with the transmembrane region of the oxytocin receptor were modelled in order to explain the selective binding of oxytocin and vasopressin. Three sites of interaction in the receptors were identified by sequence comparison and model building. Both receptors share one site, which is formed by glutamine residues. This site binds the Asn-5 common to both hormones. The second site is a specific hydrophobic pocket formed by isoleucine and phenylalanine residues. A third interaction is between a conserved tyrosine and the glutamine of vasopressin and oxytocin. The model suggests that one receptor residue in the transmembrane region is responsible for the specificity of the receptors. The model may be used in the rational design of non peptide analogues for the hormones.