High Resolution Structural Characterization of A尾42 Amyloid Fibrils by Magic Angle Spinning NMR

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• 作者：Michael T. Colvin ; Robert Silvers ; Birgitta Frohm ; Yongchao Su ; Sara Linse ; Robert G. Griffin
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：June 17, 2015
• 年：2015
• 卷：137
• 期：23
• 页码：7509-7518
• 全文大小：866K
• ISSN：1520-5126

文摘

The presence of amyloid plaques composed of amyloid beta (A尾) fibrils is a hallmark of Alzheimer鈥檚 disease (AD). The A尾 peptide is present as several length variants with two common alloforms consisting of 40 and 42 amino acids, denoted A尾_1鈥?0 and A尾_1鈥?2, respectively. While there have been numerous reports that structurally characterize fibrils of A尾_1鈥?0, very little is known about the structure of amyloid fibrils of A尾_1鈥?2, which are considered the more toxic alloform involved in AD. We have prepared isotopically ¹³C/¹⁵N labeled A尾_M01鈥?2 fibrils in vitro from recombinant protein and examined their ¹³C鈥?sup>13C and ¹³C鈥?sup>15N magic angle spinning (MAS) NMR spectra. In contrast to several other studies of A尾 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 A尾_M01鈥?2 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鈥?sup>13C, ¹³C鈥?sup>15N MAS NMR experiments for rigid residues along with J-based 2D TOBSY experiments for dynamic residues. We find that the first 鈭? residues are dynamic and most efficiently detected in a J-based TOBSY spectrum. In contrast, residues 16鈥?2 are easily observed in cross-polarization experiments and most likely form the amyloid core. Calculation of 蠄 and 蠁 dihedral angles from the chemical shift assignments indicate that 4 尾-strands are present in the fibril鈥檚 secondary structure.