title: Crystal structures of [Met5] and [(4-bromo)Phe4,Met5]enkephalins: formation of a dimeric antiparallel beta-structure.
abstract: The crystal structure of [(4-bromo)Phe4,Met5]enkephalin (Tyr-Gly-Gly-(4-bromo)-Phe-Met) shows two independent molecular conformations. The molecules are arranged in parallel in a head-to-tail fashion and form an antiparallel beta-sheet structure involving intermolecular hydrogen bonds. This dimeric beta-structure is also observed in the [Met5]enkephalin crystal, in spite of their different crystal packing environments, which shows the energetic stability of this molecular conformation. The three-dimensional similarity between the dimeric beta-structure and the beta-turn form is discussed in the relation to the opioid delta and mu receptors.
mesh_terms: D003461:Crystallography; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D004744:Enkephalin, Methionine; C041080:enkephalin-Met, 4'-bromo-Phe(4)-