Preferential conformation of the endogenous opiate-like pentapeptide met-enkephalin in DMSO-d₆ solution determined by high field ¹H NMR

Abstract

A preferential conformation of the endogenous opiate-like pentapeptide Met-Enkephalin in DMSO-d₆ solution was proposed from high field ¹H NMR experiments at variable temperature and complete analysis of the coupling constants in relation with conformational energy steric maps. This conformation is characterized by a highly folded secondary structure with a β_I turn involving a head-to-tail interaction and a quasi-axial position of the methionine side chain. The N-terminal Tyr-Gly moiety which exhibits a relative degree of freedom shows all the steric requirements found in opiates for a stereospecific interaction with the receptor. All these results are discussed in relation with the physicochemical and biological properties of opiate-like peptides.