Department of Biochemical Engineering and Key Laboratory of Systems Bioengineering of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
J Phys Chem B. 2012 Jun 21;116(24):7040-7. doi: 10.1021/jp300171h. Epub 2012 May 31.
Considerable experimental evidence indicates that trehalose can counteract the denaturing effects of urea on proteins. However, its molecular mechanism remains unknown due to the limitations of current experimental techniques. Herein, molecular dynamics simulations were performed to investigate the counteracting effects of trehalose against urea-induced denaturation of chymotrypsin inhibitor 2. The simulations indicate that the protein unfolds in 8 mol/L urea, but at the same condition the protein retains its native structure in the ternary solution of 8 mol/L urea and 1 mol/L trehalose. It is confirmed that the preferential exclusion of trehalose from the protein surface is the origin of its counteracting effects. It is found that trehalose binds urea via hydrogen bonds, so urea molecules are also expelled from the protein surface along with the preferential exclusion of trehalose. The exclusion of urea from the protein surface leads to the alleviation of the Lennard-Jones interactions between urea and the hydrophobic side chains of the protein in the ternary solution. In contrast, the electrostatic interactions between urea and the protein change little in the presence of trehalose because the decrease in the electrostatic interactions between urea and the protein backbone is canceled by the increase in the electrostatic interactions between urea and the charged side chains of the protein. The results have provided molecular explanations for the counteraction of urea-induced protein denaturation by trehalose.
大量实验证据表明，海藻糖可以对抗尿素对蛋白质的变性作用。然而，由于当前实验技术的限制，其分子机制仍不清楚。本文通过分子动力学模拟研究了海藻糖对胰凝乳蛋白酶抑制剂 2 脲变性的拮抗作用。模拟表明，在 8mol/L 尿素中，蛋白质会发生展开，但在同样的条件下，蛋白质在 8mol/L 尿素和 1mol/L 海藻糖的三元溶液中保留其天然结构。证实了海藻糖优先从蛋白质表面排除是其拮抗作用的起源。研究发现，海藻糖通过氢键与尿素结合，因此随着海藻糖的优先排除，尿素分子也从蛋白质表面被逐出。尿素从蛋白质表面的排除导致在三元溶液中减轻了尿素与蛋白质疏水性侧链之间的伦纳德-琼斯相互作用。相比之下，在有海藻糖存在的情况下，尿素与蛋白质之间的静电相互作用变化不大，因为尿素与蛋白质骨架之间的静电相互作用的减少被尿素与蛋白质带电侧链之间的静电相互作用的增加所抵消。研究结果为海藻糖拮抗尿素诱导的蛋白质变性提供了分子解释。
