We describe de novo-designed α-helical barrels (αHBs) that bind and discriminate between lipophilic biologically active molecules. αHBs have five or more α-helices arranged around central hydrophobic channels the diameters of which scale with oligomer state. We show that pentameric, hexameric, and heptameric αHBs bind the environmentally sensitive dye 1,6-diphenylhexatriene (DPH) in the micromolar range and fluoresce. Displacement of the dye is used to report the binding of nonfluorescent molecules: palmitic acid and retinol bind to all three αHBs with submicromolar inhibitor constants; farnesol binds the hexamer and heptamer; but β-carotene binds only the heptamer. A co-crystal structure of the hexamer with farnesol reveals oriented binding in the center of the hydrophobic channel. Charged side chains engineered into the lumen of the heptamer facilitate binding of polar ligands: a glutamate variant binds a cationic variant of DPH, and introducing lysine allows binding of the biosynthetically important farnesol diphosphate.

中文翻译：

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De Novo设计的α-螺旋桶作为小分子的受体

我们描述从头设计的α螺旋桶（αHBs），可结合并区分亲脂性生物活性分子。αHBs具有五个或多个围绕中心疏水通道排列的α螺旋，其直径随低聚物状态成比例增加。我们表明，五聚体，六聚体和七聚体αHBs在微摩尔范围内结合环境敏感的染料1,6-二苯基己三烯（DPH）并发出荧光。染料的置换用于报告非荧光分子的结合：棕榈酸和视黄醇以亚微摩尔抑制剂常数结合所有三个αHBs。法尼醇结合六聚体和七聚体；但β-胡萝卜素仅与七聚体结合。六聚体与法尼醇的共晶体结构揭示了在疏水通道中心的定向结合。