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首页> 外文期刊>The FEBS journal >Crystal structures of open and closed forms of cyclo/maltodextrin-binding protein
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Crystal structures of open and closed forms of cyclo/maltodextrin-binding protein

机译：环/麦芽糊精结合蛋白的开放和闭合形式的晶体结构

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The crystal structures of Thermoactinomyces vulgaris cyclo/maltodextrin-binding protein (TvuCMBP) complexed with l-cyclodextrin (l-CD), o-cyclodextrin (o-CD) and maltotetraose (G4) have been determined. A common functional conformational change among all solute-binding proteins involves switching from an open form to a closed form, which facilitates transporter binding. Escherichia coli maltodextrin-binding protein (EcoMBP), which is structurally homologous to TvuCMBP, has been determined to adopt the open form when complexed with o-CD and the closed form when bound to G4. Here, we show that, unlike EcoMBP, TvuCMBP-l-CD and TvuCMBP-o-CD adopt the closed form when complexed, whereas TvuCMBP-G4 adopts the open form. Only two glucose residues are evident in the TvuCMBP-G4 structure, and these bind to the C-domain of TvuCMBP in a manner similar to the way in which maltose binds to the C-domain of EcoMBP. The superposition of TvuCMBP-l-CD, TvuCMBP-o-CD and TvuCMBP-d-CD shows that the positions and the orientations of three glucose residues in the cyclodextrin molecules overlay remarkably well. In addition, most of the amino acid residues interacting with these three glucose residues also participate in interactions with the two glucose residues in TvuCMBP-G4, regardless of whether the protein is in the closed or open form. Our results suggest that the mechanisms by which TvuCMBP changes from the open to the closed conformation and maintains the closed form appear to be different from those of EcoMBP, despite the fact that the amino acid residues responsible for the initial binding of the ligands are well conserved between TvuCMBP and EcoMBP.
机译：已经确定了与1-环糊精（1-CD），邻-环糊精（o-CD）和麦芽四糖（G4）复合的寻常嗜热放线菌环/麦芽糊精结合蛋白（TvuCMBP）的晶体结构。所有溶质结合蛋白中常见的功能构象变化涉及从开放形式转换为封闭形式，这有利于转运蛋白结合。在结构上与TvuCMBP同源的大肠杆菌麦芽糖糊精结合蛋白（EcoMBP）已确定与o-CD复合时采用开放形式，与G4结合时采用封闭形式。在这里，我们表明，与EcoMBP不同，TvuCMBP-1-CD和TvuCMBP-o-CD在复合时采用封闭形式，而TvuCMBP-G4采用开放形式。 TvuCMBP-G4结构中只有两个葡萄糖残基是显而易见的，它们以类似于麦芽糖结合EcoMBP C域的方式结合到TvuCMBP C域。 TvuCMBP-1-CD，TvuCMBP-o-CD和TvuCMBP-d-CD的叠加表明，环糊精分子中三个葡萄糖残基的位置和方向重叠得很好。另外，与该三个葡萄糖残基相互作用的大多数氨基酸残基也参与与TvuCMBP-G4中的两个葡萄糖残基的相互作用，而不管蛋白质是封闭形式还是开放形式。我们的结果表明，尽管负责配体初始结合的氨基酸残基非常保守，但TvuCMBP从开放构象变化为封闭构象并保持封闭形式的机制似乎与EcoMBP的机制不同。在TvuCMBP和EcoMBP之间。

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