Mapping Aβ amyloid fibril secondary structure using scanning proline mutagenesis
Mapping Aβ amyloid fibril secondary structure using scanning proline mutagenesis
复制标题
DOI：
10.1016/j.jmb.2003.11.008
复制
发表时间：
2004-01-16
影响因子：
5.6
通讯作者：
Wetzel, R
中科院分区：
文献类型：
--
作者：
Williams, AD;Portelius, E;Wetzel, R
尽管由阿尔茨海默氏病淀粉样蛋白肽 Abeta 形成的淀粉样蛋白原纤维富含交叉 β 折叠，但当该肽掺入淀粉样蛋白时，它也可能表现出转角和非结构化区域。我们生成了一系列 Abeta(1-40) 的单脯氨酸替换突变体，并测定了由这些突变体形成的淀粉样原纤维的热力学稳定性，以表征 Abeta 序列的不同残基位置对脯氨酸替换的敏感性。结果表明，当 Abeta 肽与淀粉样原纤维结合时，会折叠成包含三个高度结构化片段的构象，这些片段由连续的序列元件 15-21、24-28 和 31-36 组成，这些片段对脯氨酸替代敏感，并且可能包括原纤维的 β-折叠部分。对脯氨酸替代相对不敏感的残基分为两类：（a）残基 1-14 和 37-40 可能存在于从富含 β 折叠的淀粉样蛋白核心中挤出的相对非结构化的柔性元件中； (b) 残基 22、23、29 和 30 可能占据这三个结构元件之间的转角位置。尽管不稳定，但氢-氘交换和其他分析表明，由 Abeta(1-40) 脯氨酸突变体形成的原纤维在结构上与野生型原纤维非常相似。然而有趣的是，一些脯氨酸突变使原纤维不稳定，同时增加了免受氢交换影响的酰胺质子的数量。这表明淀粉样原纤维的稳定性不是像球状蛋白那样完全由氢键β-折叠的形成驱动，而是通过稳定力和去稳定力的平衡来实现。脯氨酸扫描数据与淀粉样蛋白原丝结构模型最兼容，该模型松散地类似于平行β-螺旋折叠基序，使得每个Abeta(15-36)核心区域占据棱柱状、氢键键合肽堆的单层。 (C) 2003 Elsevier Ltd. 保留所有权利。
Although the amyloid fibrils formed from the Alzheimer's disease amyloid peptide Abeta are rich in cross-beta sheet, the peptide likely also exhibits turn and unstructured regions when it becomes incorporated into amyloid. We generated a series of single-proline replacement mutants of Abeta(1-40) and determined the thermodynamic stabilities of amyloid fibrils formed from these mutants to characterize the susceptibility of different residue positions of the Abeta sequence to proline substitution. The results suggest that the Abeta peptide, when engaged in the amyloid fibril, folds into a conformation containing three highly structured segments, consisting of contiguous sequence elements 15-21, 24-28, and 31-36, that are sensitive to proline replacement and likely to include the beta-sheet portions of the fibrils. Residues relatively insensitive to proline replacement fall into two groups: (a) residues 1-14 and 37-40 are likely to exist in relatively unstructured, flexible elements extruded from the beta-sheet-rich amyloid core; (b) residues 22, 23, 29 and 30 are likely to occupy turn positions between these three structured elements. Although destabilized, fibrils formed from Abeta(1-40) proline mutants are very similar in structure to wild-type fibrils, as indicated by hydrogen- deuterium exchange and other analysis. Interestingly, however, some proline mutations destabilize fibrils while at the same time increasing the number of amide protons protected from hydrogen exchange. This suggests that the stability of amyloid fibrils, rather than being driven exclusively by the formation of H-bonded beta-sheet, is achieved, as in globular proteins, through a balance of stabilizing and destabilizing forces. The proline scanning data are most compatible with a model for amyloid protofilament structure loosely resembling the parallel beta-helix folding motif, such that each Abeta(15-36) core region occupies a single layer of a prismatic, H-bonded stack of peptides. (C) 2003 Elsevier Ltd. All rights reserved.