Theoretical studies on pro-leu-gly-nh2 conformation.

Classical potential function calculations were carried out on the hypothalamic factor Pro-Leu-Gly-NH2. The results indicate that the proposed 10-membered, hydrogen-bonded beta-turn conformation of this tripeptide is a strongly preferred structure. Its stability appears to be inherent in the rather rigid backbone conformation of the leucine residue rather than the hydrogen bond between the carboxamide proton of glycinamide and the C=O of the proline moiety; the glycinamide has little influence on the phi-psi of the leucine backbone structure. The type II beta-turn structure of the Pro-Leu-Gly-NH2 is preferred.