Crowding and hydration effects on protein conformation: A study with sol-gel encapsulated proteins
Crowding and hydration effects on protein conformation: A study with sol-gel encapsulated proteins
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DOI：
10.1006/jmbi.2001.5166
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发表时间：
2001-12-07
影响因子：
5.6
通讯作者：
Valentine, JS
中科院分区：
文献类型：
--
作者：
Eggers, DK;Valentine, JS
我们正在开发一个实验系统，用于测试大分子拥挤和分子限制对蛋白质结构的影响。在本研究中，溶剂对两种蛋白质的二级结构的影响进行了研究，通过圆二色性封装后的二氧化硅玻璃基质的水合孔的溶胶-凝胶法。在未折叠的构象的变化进行了分析后，与天然渗透剂，短链醇，聚乙二醇，和一个完整的系列的霍夫迈斯特阳离子的水溶液平衡的封装apomyoglobin和减少血清白蛋白。在许多情况下，通过添加在不存在玻璃的情况下对蛋白质没有影响的浓度的溶质来增加包封的蛋白质的α-螺旋含量。从水结构的角度对结果进行了讨论。我们认为，扰动水在二氧化硅界面导致的平均自由能的增加，因此，减少了玻璃基质内的疏水效应的强度和不稳定的构象封装的蛋白质的散装水相。我们建议，溶质可以增加疏水效应的强度，并影响折叠平衡，而不直接与蛋白质相互作用。一个假设是提供了明显的悖论，kosmotropic（强水结合）阴离子有利于天然蛋白质结构，而离液（弱水结合）阳离子增强天然蛋白质结构。封装的结果表明，大分子拥挤和分子限制伴随着水合作用，可能会反对或加强排除体积对蛋白质结构的稳定作用，这取决于拥挤剂的表面化学性质及其对散装水结构的影响。在拥挤的环境中的活细胞，排除体积效应，表面诱导的水结构，和兼容的溶质预计将补充蛋白质折叠的主导力量。(C)北京：科学出版社.
We are developing an experimental system for testing the effects of macromolecular crowding and molecular confinement on protein structure. In the present study, solvent effects on the secondary structure of two proteins were examined by circular dichroism following encapsulation in the hydrated pores of a silica glass matrix by the sol-gel method. Changes in the unfolded conformations of encapsulated apomyoglobin and reduced serum albumin were analyzed after equilibration with aqueous solutions of natural osmolytes, short-chain alcohols, polyethylene glycol, and a complete series of Hofmeister cations. In many instances, the alpha-helical content of the encapsulated protein was increased by addition of solutes at concentrations that have no effect on the protein in the absence of the glass. The results are discussed from the perspective of water structure. We argue that perturbed water at the silica interface causes an increase in the average free energy of the bulk water phase which, consequently, diminishes the strength of the hydrophobic effect inside the glass matrix and destabilizes the conformation of encapsulated proteins. We propose that solutes can increase the strength of the hydrophobic effect and influence folding equilibria without directly interacting with the protein. A hypothesis is provided for the apparent paradox that kosmotropic (strongly water binding) anions favor native protein structure, whereas chaotropic (weakly water binding) cations enhance native protein structure. The encapsulation results suggest that macromolecular crowding and molecular confinement are accompanied by hydration effects that may oppose or potentiate the stabilizing effects of excluded volume on protein structure, depending on the surface chemistry of the crowding agent and its influence on bulk water structure. In the crowded environment of a living cell, excluded volume effects, surface-induced water structure, and compatible solutes are expected to complement the dominant forces in protein folding. (C) 2001 Academic Press.