Oligomeric assembly of native-like precursors precedes amyloid formation by β-2 microglobulin
Oligomeric assembly of native-like precursors precedes amyloid formation by β-2 microglobulin
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DOI：
10.1021/bi049792q
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发表时间：
2004-06-22
期刊：
影响因子：
2.9
通讯作者：
Miranker, AD
中科院分区：
文献类型：
--
作者：
Eakin, CM;Attenello, FJ;Miranker, AD
β-2-微球蛋白（β2m）以淀粉样纤维的形式沉积，会导致接受血液透析治疗的肾衰竭患者出现衰弱性并发症。在体外，野生型 beta2m 可在生理条件下通过暴露于生物医学相关浓度的 Cu2+ 转化为淀粉样蛋白。在这项工作中，我们对纤维形成之前的时间点β2m的结构和寡聚变化进行了比较测量。我们的结果表明 Cu2+ 介导单体活化状态的形成，然后形成离散的二聚中间体。然后，二聚中间体组装成四聚体和六聚体形式，在其自身形成的时间尺度（<1小时）上几乎没有表现出额外的寡聚化。淀粉样纤维的形成从这些中间状态开始，但时间尺度更长（> 1周）。尽管 Cu2+ 对于这些中间体的生成和稳定是必需的，但对于成熟淀粉样纤维的稳定性来说并不是必需的。这表明 Cu2+ 通过诱导寡聚体形成而充当淀粉样变性的起始因子。 H-1 NMR 和近紫外圆二色性用于确定低聚中间体在结构上与天然类似。 β2m 淀粉样蛋白中间体的天然样结构和离散寡聚体大小表明该蛋白质通过结构域交换形成原纤维。
The deposition of beta-2-microglobulin (beta2m) as amyloid fibers results in debilitating complications for renal failure patients who are treated by hemodialysis. In vitro, wild-type beta2m can be converted to amyloid under physiological conditions by exposure to biomedically relevant concentrations of Cu2+. in this work, we have made comparative measurements of the structural and oligomeric changes in beta2m at time points preceding fibrillogenesis. Our results show Cu2+ mediates the formation of a monomeric, activated state followed by the formation of a discrete dimeric intermediate. The dimeric intermediates then assemble into tetra- and hexameric forms which display little additional oligomerization on the time scales of their own formation (< 1 h). Amyloid fiber formation progresses from these intermediate states but on much longer time scales (> 1 week). Although Cu2+ is necessary for the generation and stabilization of these intermediates, it is not required for the stability of mature amyloid fibers. This suggests that Cu2+ acts as an initiating factor of amyloidosis by inducing oligomer formation. H-1 NMR and near-UV circular dichroism are used to establish that oligomeric intermediates are native-like in structure. The native-like structure and discrete oligomeric size of beta2m amyloid intermediates suggest that this protein forms fibrils by structural domain swapping.