Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, Nebraska, United States.
Sci Rep. 2017 May 24;7(1):2344. doi: 10.1038/s41598-017-02454-0.
Structural investigations have revealed that β hairpin structures are common features in amyloid fibrils, suggesting that these motifs play an important role in amyloid assembly. To test this hypothesis, we characterized the effect of the hairpin fold on the aggregation process using a model β hairpin structure, consisting of two Aβ(14-23) monomers connected by a turn forming YNGK peptide. AFM studies of the assembled aggregates revealed that the hairpin forms spherical structures whereas linear Aβ(14-23) monomers form fibrils. Additionally, an equimolar mixture of the monomer and the hairpin assembles into non-fibrillar aggregates, demonstrating that the hairpin fold dramatically changes the morphology of assembled amyloid aggregates. To understand the molecular mechanism underlying the role of the hairpin fold on amyloid assembly, we performed single-molecule probing experiments to measure interactions between hairpin and monomer and two hairpin complexes. The studies reveal that the stability of hairpin-monomer complexes is much higher than hairpin-hairpin complexes. Molecular dynamics simulations revealed a novel intercalated complex for the hairpin and monomer and Monte Carlo modeling further demonstrated that such nano-assemblies have elevated stability compared with stability of the dimer formed by Aβ(14-23) hairpin. The role of such folding on the amyloid assembly is also discussed.
结构研究表明β发夹结构是淀粉样纤维中的常见特征，这表明这些基序在淀粉样聚集中发挥重要作用。为了验证这一假说，我们使用由两个通过形成 YNGK 肽的环连接的 Aβ(14-23)单体组成的模型β发夹结构，表征了发夹折叠对聚集过程的影响。组装聚集体的 AFM 研究表明，发夹形成球形结构，而线性 Aβ(14-23)单体形成纤维。此外，单体和发夹的等摩尔混合物组装成无纤维状聚集物，表明发夹折叠显著改变了聚集的淀粉样纤维的形态。为了了解发夹折叠对淀粉样聚集作用的分子机制，我们进行了单分子探测实验，以测量发夹和单体以及两个发夹复合物之间的相互作用。研究表明，发夹-单体复合物的稳定性远高于发夹-发夹复合物。分子动力学模拟揭示了发夹和单体的新型插入复合物，蒙特卡罗建模进一步表明，与由 Aβ(14-23)发夹形成的二聚体的稳定性相比，这种纳米组装具有更高的稳定性。还讨论了这种折叠对淀粉样纤维组装的作用。
