Local interactions drive the formation of nonnative structure in the denatured state of human alpha-lactalbumin: a high resolution structural characterization of a peptide model in aqueous solution.
Local interactions drive the formation of nonnative structure in the denatured state of human alpha-lactalbumin: a high resolution structural characterization of a peptide model in aqueous solution.
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局部相互作用驱动人α-乳清蛋白变性状态下非天然结构的形成：水溶液中肽模型的高分辨率结构表征。
DOI：
10.1021/bi990320z
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Raleigh,DP
中科院分区：
文献类型：
--
作者：
Demarest,SJ;Hua,Y;Raleigh,DP
有少数源自蛋白质的肽倾向于在水溶液中采用与其在母体蛋白质中具有的结构相似的结构。单独采用稳定的非天然结构的蛋白质片段的例子要少得多。了解非天然相互作用如何参与蛋白质折叠对于我们理解该主题至关重要。在这里，我们表明，与蛋白质 α-乳清蛋白的残基 101−111 相对应的一个由 11 个氨基酸组成的小肽在水溶液中分离时具有显着的结构。该肽已通过 1 H NMR 进行表征，并使用 170 ROE 衍生约束来计算结构。计算得出残基 101−107 的单一高分辨率结构，该结构在主链和侧链构象中都是非天然的。在pH 6.5的晶体结构中，残基101-105呈不规则的转角构象，残基106-111形成α-螺旋。在pH 4.2晶体结构中，残基101-105形成α-螺旋，残基106-111形成环状结构。这两种结构都与我们的肽采用的构象显着不同。肽模型中的结构主要是局部侧链相互作用的结果，迫使主链在残基 103−106 中采用非天然 310/转角结构。将水溶液中的结构与30%三氟乙醇(TFE)中的结构进行比较，观察到明显的差异。特别是，侧链相互作用之一（涉及残基 101−105 的疏水簇）在两种溶剂中是不同的，并且残基 107−111 在 30% TFE 中明显更加有序。讨论了非天然结构对 α-乳清蛋白折叠的影响。
There are a small number of peptides derived from proteins that have a propensity to adopt structure in aqueous solution which is similar to the structure they possess in the parent protein. There are far fewer examples of protein fragments which adopt stable nonnative structures in isolation. Understanding how nonnative interactions are involved in protein folding is crucial to our understanding of the topic. Here we show that a small, 11 amino acid peptide corresponding to residues 101−111 of the protein α-lactalbumin is remarkably structured in isolation in aqueous solution. The peptide has been characterized by1H NMR, and 170 ROE-derived constraints were used to calculate a structure. The calculations yielded a single, high-resolution structure for residues 101−107 that is nonnative in both the backbone and side-chain conformations. In the pH 6.5 crystal structure, residues 101−105 are in an irregular turn-like conformation and residues 106−111 form an α-helix. In the pH 4.2 crystal structure, residues 101−105 form an α-helix, and residues 106−111 form a loopike structure. Both of these structures are significantly different from the conformation adopted by our peptide. The structure in the peptide model is primarily the result of local side-chain interactions that force the backbone to adopt a nonnative 310/turn-like structure in residues 103−106. The structure in aqueous solution was compared to the structure in 30% trifluoroethanol (TFE), and clear differences were observed. In particular, one of the side-chain interactions, a hydrophobic cluster involving residues 101−105, is different in the two solvents and residues 107−111 are considerably more ordered in 30% TFE. The implications of the nonnative structure for the folding of α-lactalbumin is discussed.