title: Methionine enkephalin and isosteric analogues. Part II.: Receptor conformation of methionine enkephalin.
abstract: Biological activities are reported for two different types of analogues of methionine enkephalin. Cyclic analogues, bridged between the amino- and carboxy- terminals of the parent peptide, are inactive. In contrast, significant levels of activity are displayed by linear isosterically modified analogues in which the Tyr1-Gly2 peptide bond is replaced by either -CH2NH- or -CH2CH2-. Similar replacements of the Gly2-Gly3 peptide bond yield compounds with much reduced potency. These modifications serve as useful probes of the receptor conformation. Based on these findings, a model is proposed for interaction between enkephalin and its receptor.
mesh_terms: D000818:Animals; D004723:Endorphins / Q000378:metabolism*; D004744:Enkephalin, Methionine; D004745:Enkephalins / Q000378:metabolism*; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism; D066298:In Vitro Techniques; D051379:Mice; D011487:Protein Conformation; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*
chemical_list: D004723:Endorphins; D004745:Enkephalins; D011957:Receptors, Opioid; D004744:Enkephalin, Methionine