Effects of Polymer Hydrophobicity on Protein Structure and Aggregation Kinetics in Crowded Milieu
Effects of Polymer Hydrophobicity on Protein Structure and Aggregation Kinetics in Crowded Milieu
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DOI：
10.1021/acs.biochem.5b00116
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发表时间：
2015-05-19
期刊：
影响因子：
2.9
通讯作者：
Uversky, Vladimir N.
中科院分区：
文献类型：
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作者：
Breydo, Leonid;Sales, Amanda E.;Uversky, Vladimir N.
我们研究了不同疏水度的水溶性聚合物对蛋白质折叠和聚集的影响。我们选择的聚合物是聚乙二醇（PEG）和UCON（乙二醇和丙二醇的1：1共聚物）。UCON中额外甲基的存在使其比PEG更疏水。我们早期的分析揭示了类似大小的PEG和UCON在其溶液中水的溶剂性质方面产生不同的变化，并诱导形态上不同的α-突触核蛋白聚集体[Ferreira，L. A等人（2015）水介质的溶剂性质在大分子拥挤效应中的作用。J. Biomol. Struct. Dyn，in press].为了提高我们对在拥挤环境中定义蛋白质行为的分子机制的理解，我们测试了这些聚合物对10种蛋白质[5种折叠蛋白质，2种杂合蛋白质;即，包含有序和无序结构域的蛋白质，以及三种内在无序蛋白质（IDP）]和胰岛素和α-突触核蛋白的聚集动力学。我们发现这两种聚合物对折叠和杂交蛋白的二级和三级结构的影响是相当有限的，在某些情况下观察到轻微的展开。溶剂的芳香族残基的可及性显着增加的大多数研究的蛋白质在UCON的存在下，但没有PEG。PEG也促进蛋白质聚集成淀粉样纤维，而UCON促进聚集成淀粉样寡聚体。这些结果表明，即使聚合物结构的相对较小的变化也会导致该聚合物对蛋白质折叠和聚集的影响发生显著变化。这表明蛋白质折叠，特别是聚集对其他大分子的存在高度敏感，排除的体积效应不足以描述它们的作用。
We examined the effects of water-soluble polymers of various degrees of hydrophobicity on the folding and aggregation of proteins. The polymers we chose were polyethylene glycol (PEG) and UCON (1:1 copolymer of ethylene glycol and propylene glycol). The presence of additional methyl groups in UCON makes it more hydrophobic than PEG. Our earlier analysis revealed that similarly sized PEG and UCON produced different changes in the solvent properties of water in their solutions and induced morphologically different alpha-synuclein aggregates [Ferreira, L. A, et al. (2015) Role of solvent properties of aqueous media in macromolecular crowding effects. J. Biomol. Struct. Dyn, in press]. To improve our understanding of molecular mechanisms defining behavior of proteins in a crowded environment, we tested the effects of these polymers on secondary and tertiary structure and aromatic residue solvent accessibility of 10 proteins [five folded proteins, two hybrid proteins; le., protein containing ordered and disordered domains, and three intrinsically disordered proteins (IDPs)] and on the aggregation kinetics of insulin and alpha-synuclein. We found that effects of both polymers on secondary and tertiary structures of folded and hybrid proteins were rather limited with slight unfolding observed in some cases. Solvent accessibility of aromatic residues was significantly increased for the majority of the Studied proteins in the presence of UCON but not PEG. PEG also accelerated the aggregation of protein into amyloid fibrils, whereas UCON promoted aggregation to amyloid oligomers instead. These results indicate that even a relatively small change in polymer structure leads to a significant change in the effect of this polymer on protein folding and aggregation. This is an indication that protein folding and especially aggregation are highly sensitive to the presence of other macromolecules, and an excluded volume effect is insufficient to describe their effect.