Tertiary structure of H Pro Leu Gly NH2, the factor that inhibits release of melanocyte stimulating hormone, derived by conformational energy calculations

Conformational energy calculations were carried out on H Pro Leu Gly NH2, the factor that inhibits the release of melanocyte stimulating hormone, and its biologically active analog, H Pro Ala Gly NH2. Both peptides were found to be relatively compact molecules that retain, however, some degree of flexibility. After structure refinement, H Pro Leu Gly NH2 possesses at least three preferred compact conformations. Two of these conformations occupy rather broad and flat energy troughs, while a third occupies a narrow and deep potential energy well. This third structure, which consists of a 10 membered β turn closed by a (4→1) hydrogen bond between the proton of the trans carboxamide of Gly and the C=O of Pro, is the one that was proposed for H Pro Leu Gly NH2 in dimethylsulfoxide and was also found by X ray analysis.SCOPUS: ar.j