Preferred conformation of endomorphin-1 in aqueous and membrane-mimetic environments

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• 作者：Fiori ; Stella ; Renner ; Christian ; Cramer ; Jö ; rg ; Pegoraro ; Stefano ; Moroder ; Luis
• 关键词：opioid peptides ; μ ; -receptor ; conformation ; SDS micelles ; AOT reverse micelles ; TMSP-d₄ ; sodium 2 ; 2 ; 3 ; 3-tetradeutero-3-(trimethylsilyl)-propionate ; MBHA ; 4-methylbenzhydrylamine ; TFA ; trifluoroacetic acid ; TMS ; tetramethylsilane ; DMPG ; 1 ; 2-
• 刊名：Journal of Molecular Biology
• 出版年：1999
• 出版时间：September 6, 1999
• 年：1999
• 卷：291
• 期：1
• 页码：163-175
• 全文大小：445 K

文摘

The newly discovered endomorphin-1 (Tyr-Pro-Trp-Phe-NH₂) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH₂) are potent opioid peptides with the highest affinity and selectivity for the μ receptor among all known endogenous ligands. To investigate a possible correlation between these biological properties and the conformational preferences of the small peptides, a comparative structural analysis was performed of endomorphin-1 in aqueous buffer and in membrane-mimicking SDS and AOT normal and reverse micelles by the use of CD, FT-IR, fluorescence and ¹H-NMR spectroscopy. It is well established for opioid peptides that, independently of the receptor selectivity, the Tyr1 residue plays the role of the primary pharmacophore and that the orientation of the second aromatic pharmacophore relative to the tyrosine side-chain dictates the μ or 48;-receptor selectivity. By varying the environment of endomorphin-1 from water to the amphipathic SDS micelles and even more efficiently to the AOT reverse micelles, the display of the aromatic side-chains changes from an interaction of the Tyr1 and Phe4 residues to a switch of the Trp3 indole group into close contact with the phenolic moiety to prevent this type of interaction and to force an orientation of the Phe4 side-chain into the opposite direction. This conformational switch is accompanied by a stabilization of the cis-Pro2 isomer and the resulting spatial array of the pharmacophoric groups correlate well with the structural model of μ receptor-bound opioid peptides. The results indicate that AOT reverse micelles with a w_oof 10, where almost exclusively ordered water is secluded in the cavity, constitute with their electrostatic and hydrophobic potential an excellent mimetic of amphipathic surfaces as present on lipid bilayers and on ligand-recognition and ligand-binding sites of proteins.