Breydo Leonid, Sales Amanda E, Frege Telma, Howell Mark C, Zaslavsky Boris Y, Uversky Vladimir N
Biochemistry. 2015 May 19;54(19):2957-66. doi: 10.1021/acs.biochem.5b00116.
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 α-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; i.e., protein containing ordered and disordered domains, and three intrinsically disordered proteins (IDPs)] and on the aggregation kinetics of insulin and α-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.
我们研究了不同疏水程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（乙二醇与丙二醇的1:1共聚物）。UCON中额外甲基的存在使其比PEG更疏水。我们早期的分析表明，大小相似的PEG和UCON在其溶液中对水的溶剂性质产生了不同的变化，并诱导出形态不同的α-突触核蛋白聚集体[费雷拉，L.A.等人（2015年）水相介质的溶剂性质在大分子拥挤效应中的作用。《生物分子结构与动力学杂志》，即将发表]。为了更好地理解在拥挤环境中定义蛋白质行为的分子机制，我们测试了这些聚合物对10种蛋白质的二级和三级结构以及芳香族残基溶剂可及性的影响[5种折叠蛋白、2种杂合蛋白，即含有有序和无序结构域的蛋白，以及3种内在无序蛋白（IDP）]，以及对胰岛素和α-突触核蛋白聚集动力学的影响。我们发现，两种聚合物对折叠蛋白和杂合蛋白的二级和三级结构的影响相当有限，在某些情况下观察到轻微的去折叠。在UCON存在下，大多数研究蛋白的芳香族残基的溶剂可及性显著增加，而在PEG存在下则没有。PEG还加速了蛋白质聚集成淀粉样纤维，而UCON则促进聚集成淀粉样寡聚体。这些结果表明，即使聚合物结构发生相对较小的变化，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。这表明蛋白质折叠尤其是聚集对其他大分子的存在高度敏感，而排除体积效应不足以描述它们的影响。
