A SAXS Study of Glucagon Fibrillation
A SAXS Study of Glucagon Fibrillation
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DOI：
10.1016/j.jmb.2009.01.020
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发表时间：
2009-03-20
影响因子：
5.6
通讯作者：
Pedersen, Jan Skov
中科院分区：
文献类型：
--
作者：
Oliveira, Cristiano Luis Pinto;Behrens, Manja Annette;Pedersen, Jan Skov
蛋白质淀粉样蛋白的形成经历了许多不同的阶段。在早期阶段观察到的寡聚体物种引起了特别的兴趣，因为有证据表明它们参与细胞毒性过程，如膜透化。目前还不清楚这些低聚物是专性前体纤维或代表“死端”物种，阻碍原纤化。由于淀粉样蛋白形成过程中存在许多相互转化的物质，因此尽可能非侵入性地研究该过程是很重要的。小角X射线散射（SAXS）测量使我们能够监测不同物种种群随时间的结构变化。在这里，SAXS被用来提供一个详细的结构描述的原纤化的29个残基肽激素胰高血糖素在pH 2.5的单体和早期低聚物成熟的纤维。在几种浓度下对原纤化之前的滞后期中的伪平衡行为的研究表明，胰高血糖素以低于约5.1 mg/mL的单体形式存在，而分别在6.4和10.7 mg/mL下形成平均聚集数为约3和7的较大寡聚体。应用几种建模工具的实验数据，它表明，早期寡聚化状态可以被描述为胰高血糖素分子之间的关联。在滞后期之后，形成短的杆状原纤维（半径类似于16埃，长度> 300埃），随后生长到长度> 1000埃，并组装成长的三束成熟纤维。原纤维与被认为是胰岛素原纤维的结构核的细长寡聚体具有许多特征。我们建议，在通路上的纤维状中间体共享这种细长的形状，很容易使它们被纳入成熟的原纤维。这与环形形状形成对比，环形形状被认为参与细胞毒性膜透化，并且可能代表纤维途径的死端物质。(C)2009爱思唯尔有限公司保留所有权利。
Protein amyloid formation proceeds through a number of different stages. Oligomeric species observed at early stages have aroused particular interest because of evidence for their involvement in cytotoxic processes such as membrane permeabilization. It is unclear whether these oligomers are obligate precursors to fibrils or represent "dead-end" species that impede fibrillation. Because of the many interconverting species present during amyloid formation, it is important to study the process as non-invasively as possible. Small angle X-ray scattering (SAXS) measurements allow us to monitor structural changes in solution for a population of different species over time. Here, SAXS was used to provide a detailed structural description of the fibrillation of the 29 residue peptide hormone glucagon at pH 2.5 from the monomer and early oligomers to mature fibers. Investigation of the pseudo-equilibrium behavior in the lag phase before fibrillation at several concentrations showed that glucagon is present in a monomeric form below about 5.1 mg/mL, while larger oligomers with average aggregation numbers of about three and seven, are formed at 6.4 and 10.7 mg/mL, respectively. Applying several modeling tools to the experimental data, it is shown that the early oligomerization states can be described as associations between glucagon molecules. After the lag phase, a short rod-like protofibril (radius of similar to 16 angstrom and length > 300 angstrom) is formed and subsequently grows to > 1000 angstrom in length and assembles into long triple-bundled mature fibers. The protofibril shares many features with the elongated oligomer proposed to be the structural nucleus for insulin fibrils. We propose that on-pathway fibrillar intermediates share this elongated shape that easily allows them to be incorporated into mature fibrils. This contrasts with the annular shape, which is suggested to be involved in cytotoxic membrane permeabilization and may represent a dead-end species off the fibrillar pathway. (C) 2009 Elsevier Ltd. All rights reserved.