Structural Features and Domain Organization of Huntingtin Fibrils
Structural Features and Domain Organization of Huntingtin Fibrils
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DOI：
10.1074/jbc.m112.353839
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发表时间：
2012-09-14
影响因子：
4.8
通讯作者：
Langen, Ralf
中科院分区：
文献类型：
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作者：
Bugg, Charles W.;Isas, J. Mario;Langen, Ralf
亨廷顿蛋白的错误折叠和聚集是亨廷顿病的标志之一，但这些聚集体的整体结构以及亨廷顿蛋白错误折叠的机制仍然知之甚少。在这里，我们使用定点自旋标记和电子顺磁共振（EPR）光谱来研究在其聚谷氨酰胺（polyQ）区域含有46个谷氨酰胺残基的亨廷顿外显子1（HDx1）的结构特征。尽管 N 末端有一些残留结构，我们发现可溶性 HDx1 具有高度动态性。聚集后，polyQ 结构域变得牢固固定，表明存在显着的三级或四级堆积相互作用。自旋-自旋相互作用的分析并未显示相同残基之间的紧密接触，而这是淀粉样蛋白中常见的平行、对准结构的特征。然而，相同的残基彼此之间的距离仍然在 20 埃以内，这表明来自不同分子的 PolyQ 结构域在原纤维中接近。先前已发现原纤维中的 N 末端呈螺旋结构。我们发现这个域不仅变得结构化，而且还参与三级或四级堆积相互作用。该区域中自旋-自旋相互作用的存在表明，这种接触可以在不同分子的 N 端结构域之间进行。相比之下，C 末端结构域是动态的，包含聚脯氨酸 II 结构，并且缺乏明显的堆积相互作用。该区域必须背对原纤维的核心。总的来说，这些数据为构建 HDx1 原纤维结构模型提供了新的约束。
Misfolding and aggregation of huntingtin is one of the hallmarks of Huntington disease, but the overall structure of these aggregates and the mechanisms by which huntingtin misfolds remain poorly understood. Here we used site-directed spin labeling and electron paramagnetic resonance (EPR) spectroscopy to study the structural features of huntingtin exon 1 (HDx1) containing 46 glutamine residues in its polyglutamine ( polyQ) region. Despite some residual structuring in the N terminus, we find that soluble HDx1 is highly dynamic. Upon aggregation, the polyQ domain becomes strongly immobilized indicating significant tertiary or quaternary packing interactions. Analysis of spin-spin interactions does not show the close contact between same residues that is characteristic of the parallel, in-register structure commonly found in amyloids. Nevertheless, the same residues are still within 20 angstrom of each other, suggesting that polyQ domains from different molecules come into proximity in the fibrils. The N terminus has previously been found to take up a helical structure in fibrils. We find that this domain not only becomes structured, but that it also engages in tertiary or quaternary packing interactions. The existence of spin-spin interactions in this region suggests that such contacts could be made between N-terminal domains from different molecules. In contrast, the C-terminal domain is dynamic, contains polyproline II structure, and lacks pronounced packing interactions. This region must be facing away from the core of the fibrils. Collectively, these data provide new constraints for building structural models of HDx1 fibrils.