Crystal structures of [Met5] and [(4-bromo)Phe4,Met5]enkephalins: formation of a dimeric antiparallel beta-structure |
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Authors: | M Doi M Tanaka T Ishida M Inoue T Fujiwara K Tomita T Kimura S Sakakibara G M Sheldrick |
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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. |
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