A model for the δ‐receptor‐bound conformation of enkephalin

Sets of low-energy structures were determined by energy calculations for two cyclic analogues of enkephalin (Ek), [D-P n⁵]-Ek and [D-P n⁵]-Ek, possessing the highest specificity towards δ-opioid receptors. Comparison of mutual spatial orientations of the α-amino group and aromatic moieties of the Tyr and Phe residues permitted one to suggest a model for the δ-receptor-bound conformation of enkephalin-related peptides. The model involves a pronounced γ-like turn of the peptide backbone centred on the Gly³ residue.