Structural analysis of Alzheimer's β(1-40) amyloid:: Protofilament assembly of tubular fibrils
Structural analysis of Alzheimer's β(1-40) amyloid:: Protofilament assembly of tubular fibrils
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DOI：
10.1016/s0006-3495(98)77812-9
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发表时间：
1998-01-01
影响因子：
3.4
通讯作者：
Kirschner, DA
中科院分区：
文献类型：
--
作者：
Malinchik, SB;Inouye, H;Kirschner, DA
对淀粉样蛋白原纤维的详细结构研究可以阐明其组成多肽折叠和自组装的方式，并在阿尔茨海默病（AD）中发挥其神经毒性作用。我们以前曾报道过，当AD β-淀粉样蛋白（A β）的N-末端亲水肽的水溶液在2特斯拉的磁场中逐渐干燥时，它们形成高度取向的原纤维，非常适合X射线纤维衍射。较长的、生理学上更相关的序列如A β（1-40）不适合这样的分析，因为它们在实现定向之前具有很强的变性和聚集倾向。在寻求一种有效而廉价的方法。快速筛选的条件，可以导致更长的肽组装的原纤维的方向改善，我们在这里报告说，一小滴肽溶液的双折射可以提供相关的信息，合作包装的淀粉样蛋白纤维和他们的能力，磁取向。通过电子显微镜（阴性和阳性染色）和X射线衍射检查样品。阴性染色显示直纤维和扭曲纤维的混合物。两种类型的平均宽度近似于70埃，而后者的螺距近似于460埃。塑料包埋样品的横截面显示出类似于60埃宽的管状结构。来自这些样品的X射线衍射表明交叉β纤维图案，其特征在于在4.74埃处的强赤道反射和在8.9埃处的宽赤道反射。模拟研究表明，β链的倾斜阵列构成管状，30埃直径的原丝，这些原丝中的三到五个构成A β纤维。这种类型的结构-组织为管状纤维的原丝的多聚体阵列-类似于由较短的A β片段形成的结构（例如，A β（6-25）、A β（11-25）、A β（1-28）），表明AD淀粉样蛋白原纤维组织中的共同结构基序。
Detailed structural studies of amyloid fibrils can elucidate the way in which their constituent polypeptides are folded and self-assemble, and exert their neurotoxic effects in Alzheimer's disease (AD). We have previously reported that when aqueous solutions of the N-terminal hydrophilic peptides of AD beta-amyloid (A beta) are gradually dried in a 2-Tesla magnetic field, they form highly oriented fibrils that are well suited to x-ray fiber diffraction. The longer, more physiologically relevant sequences such as A beta(1-40) have not been amenable to such analysis, owing to their strong propensity to polymerize and aggregate before orientation is achieved. In seeking an efficient and inexpensive method for. rapid screening of conditions that could lead to improved orientation of fibrils assembled from the longer peptides, we report here that the birefringence of a small drop of peptide solution can supply information related to the cooperative packing of amyloid fibers and their capacity for magnetic orientation. The samples were examined by electron microscopy (negative and positive staining) and x-ray diffraction. Negative staining showed a mixture of straight and twisted fibers. The average width of both types was similar to 70 Angstrom, and the helical pitch of the latter was similar to 460 Angstrom. Cross sections of plastic-embedded samples showed a similar to 60-Angstrom-wide tubular structure. X-ray diffraction from these samples indicated a cross-beta fiber pattern, characterized by a strong meridional reflection at 4.74 Angstrom and a broad equatorial reflection at 8.9 Angstrom. Modeling studies suggested that tilted arrays of beta-strands constitute tubular, 30-Angstrom-diameter protofilaments, and that three to five of these protofilaments constitute the A beta fiber. This type of structure-a multimeric array of protofilaments organized as a tubular fibril-resembles that formed by the shorter A beta fragments (e.g., A beta(6-25), A beta(11-25), A beta(1-28)), suggesting a common structural motif in AD amyloid fibril organization.