Conformation of [Leu5]enkephalin from X-ray diffraction: features important for recognition at opiate receptor

The conformation of [Leu5]enkephalin is produced by a Tyr-Gly-Gly-Phe beta bend stabilized by antiparallel hydrogen bonding between tyrosine and phenylalanine. On the basis of a comparison of the observed structure with the structure of known opiate agonists, three hydrophilic and two hydrophobic regions have been identified as contributing to the recognition of the molecule at the opiate receptor site.