School of Biotechnology, Jawaharlal Nehru University, New Mehrauli Road, New Delhi 110067, India.
School of Biotechnology, Jawaharlal Nehru University, New Mehrauli Road, New Delhi 110067, India.
Biochim Biophys Acta Proteins Proteom. 2018 Oct;1866(10):1029-1042. doi: 10.1016/j.bbapap.2018.07.003. Epub 2018 Jul 9.
Polyol osmolytes accumulated in cells under stress are known to promote stability in globular proteins with respect to their increasing hydroxyl groups but their effect on the structure, stability and aggregation of intrinsically disordered proteins (IDPs) is still elusive. The lack of a natively folded structure in intrinsically disordered proteins under physiological conditions results in their aggregation and fibrillation that gives rise to a number of diseases. We have investigated the effect of a series of polyols, ethylene glycol (EG), glycerol, erythritol, xylitol and sorbitol on the fibrillation pathway of recombinant human γ-Synuclein, used as a model, for an IDP known to form fibrils that play a role in neurodegeneration and cancer. With an increase in the number of -OH groups in polyols except EG, we observe a decrease in lag time for fibrillation at equimolar concentrations, suggesting stronger preferential exclusion of polyols that promotes γ-Syn self-association and oligomerization. The polyols act early during nucleation and their diverse effect on the rate of fibrillation suggests the role of favourable solvent-side chain interactions. With increasing -OH group, polyols stabilize the natively unfolded conformation of γ-Syn under non-fibrillating conditions and delay the structural transition to characteristic β-sheet structure by forming an α-helical intermediate during fibrillation. The results, overall suggest that the effect of osmolytes on IDPs is much more complex than their effect on globular protein stability and aggregation and a fine balance between the dominant unfavourable osmolyte-peptide backbone and favourable osmolyte-charged side chain interactions would govern their stability and aggregation properties.
在应激条件下，细胞中积累的多元醇渗透物已知可促进球状蛋白稳定性增加其羟基，但它们对结构、稳定性和无规卷曲蛋白（IDP）聚集的影响仍不清楚。在生理条件下，无规卷曲蛋白缺乏天然折叠结构，导致其聚集和纤维化，从而引发多种疾病。我们研究了一系列多元醇，即乙二醇（EG）、甘油、赤藓糖醇、木糖醇和山梨糖醇，对作为 IDP 模型的重组人 γ-突触核蛋白纤维化途径的影响，该蛋白已知形成纤维，在神经退行性变和癌症中发挥作用。随着多元醇中 -OH 基团数量的增加，我们观察到等摩尔浓度下纤维化的滞后时间减少，这表明多元醇的优先排斥作用更强，促进 γ-突触核蛋白的自缔合和寡聚化。多元醇在成核早期起作用，它们对纤维化速率的不同影响表明有利的溶剂侧链相互作用的作用。随着 -OH 基团的增加，多元醇在非纤维形成条件下稳定 γ-突触核蛋白的天然无规卷曲构象，并在纤维形成过程中形成α-螺旋中间体，从而延迟向特征β-折叠结构的结构转变。总的来说，这些结果表明，渗透物对 IDP 的影响比它们对球状蛋白稳定性和聚集的影响复杂得多，在主导不利的渗透物-肽主链和有利的渗透物-带电侧链相互作用之间的精细平衡将控制它们的稳定性和聚集特性。
