High resolution structural characterization of Aβ42 amyloid fibrils by magic angle spinning NMR.
High resolution structural characterization of Aβ42 amyloid fibrils by magic angle spinning NMR.
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DOI：
10.1021/jacs.5b03997
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发表时间：
2015-06-17
影响因子：
15
通讯作者：
Griffin RG
中科院分区：
文献类型：
--
作者：
Colvin MT;Silvers R;Frohm B;Su Y;Linse S;Griffin RG
由淀粉样蛋白β（Aβ）原纤维组成的淀粉样蛋白斑块的存在是阿尔茨海默病（AD）的标志。Aβ肽以几种长度变体存在，有两种常见的同种异型，分别由40和42个氨基酸组成，分别表示为Aβ1-40和Aβ1-42。虽然有许多报告描述了Aβ1-40纤维的结构特征，但对Aβ1-42淀粉样纤维的结构知之甚少，A β1-42被认为是AD中毒性更大的同种异型。我们在体外从重组蛋白中制备了13 C/15 N标记的AβM01-42纤维，并检测了它们的13 C-13 C和13 C-15 N魔角自旋（MAS）NMR谱。与其他几项Aβ原纤维的研究相比，我们观察到具有优异分辨率和单组化学位移的光谱，表明存在单一原纤维形态。我们报告了AβM01-42原纤维的初步结构表征，利用43个残基中38个残基的13 C和15 N位移分配，包括主链和侧链，通过一系列基于交叉极化的2D和3D 13 C-13 C，13 C-15 N MAS NMR实验（刚性残基）沿着基于J的2D TOBSY实验（动态残基）获得。我们发现，第一个105个残基是动态的，最有效地检测J-基于TOBSY光谱。相反，残基16-42在交叉极化实验中容易观察到，并且最有可能形成淀粉样蛋白核心。根据化学位移归属计算β和φ二面角表明，在原纤维的二级结构中存在4条β链。
The presence of amyloid plaques composed of amyloid beta (Aβ) fibrils is a hallmark of Alzheimer’s disease (AD). The Aβ peptide is present as several length variants with two common alloforms consisting of 40 and 42 amino acids, denoted Aβ1–40 and Aβ1–42, respectively. While there have been numerous reports that structurally characterize fibrils of Aβ1–40, very little is known about the structure of amyloid fibrils of Aβ1–42, which are considered the more toxic alloform involved in AD. We have prepared isotopically 13C/15N labeled AβM01–42 fibrils in vitro from recombinant protein and examined their 13C–13C and 13C–15N magic angle spinning (MAS) NMR spectra. In contrast to several other studies of Aβ fibrils, we observe spectra with excellent resolution and a single set of chemical shifts, suggesting the presence of a single fibril morphology. We report the initial structural characterization of AβM01–42 fibrils utilizing 13C and 15N shift assignments of 38 of the 43 residues, including the backbone and side chains, obtained through a series of cross-polarization based 2D and 3D 13C–13C, 13C–15N MAS NMR experiments for rigid residues along with J-based 2D TOBSY experiments for dynamic residues. We find that the first ∼5 residues are dynamic and most efficiently detected in a J-based TOBSY spectrum. In contrast, residues 16–42 are easily observed in cross-polarization experiments and most likely form the amyloid core. Calculation of ψ and φ dihedral angles from the chemical shift assignments indicate that 4 β-strands are present in the fibril’s secondary structure.