Martin Stephen R, Esposito Veronica, De Los Rios Paolo, Pastore Annalisa, Temussi Piero Andrea
National Institute for Medical Research, The Ridgeway, London NW7 1AA U.K.
J Am Chem Soc. 2008 Jul 30;130(30):9963-70. doi: 10.1021/ja803280e. Epub 2008 Jul 2.
Although alcohols are well-known to be protein denaturants when present at high concentrations, their effect on proteins at low concentrations is much less well characterized. In this paper, we present a study of the effects of alcohols on protein stability using Yfh1, the yeast ortholog of the human protein frataxin. Exploiting the unusual property of this protein of undergoing cold denaturation around 0 degrees C without any ad hoc destabilization, we determined the stability curve on the basis of both high and low temperature unfolding in the presence of three commonly used alcohols: trifluoroethanol, ethanol, and methanol. In all cases, we observed an extended temperature range of protein stability as determined by a modest increase of the high temperature of unfolding but an appreciable decrease in the low temperature of unfolding. On the basis of simple thermodynamic considerations, we are able to interpret the literature on the effects of alcohols on proteins and to generalize our findings. We suggest that alcohols, at low concentration and physiological pH, stabilize proteins by greatly widening the range of temperatures over which the protein is stable. Our results also clarify the molecular mechanism of the interaction and validate the current theoretical interpretation of the mechanism of cold denaturation.
尽管众所周知，高浓度酒精是蛋白质变性剂，但它们在低浓度时对蛋白质的影响却鲜为人知。在本文中，我们利用人类蛋白质frataxin的酵母同源物Yfh1，对酒精对蛋白质稳定性的影响进行了研究。利用该蛋白质在0摄氏度左右会发生冷变性且无需任何特殊去稳定化的特殊性质，我们在三种常用酒精（三氟乙醇、乙醇和甲醇）存在的情况下，根据高温和低温展开情况确定了稳定性曲线。在所有情况下，我们观察到蛋白质稳定性的温度范围有所扩展，这是由高温展开温度适度升高但低温展开温度明显降低所决定的。基于简单的热力学考虑，我们能够解释关于酒精对蛋白质影响的文献，并推广我们的发现。我们认为，在低浓度和生理pH值下，酒精通过极大地拓宽蛋白质稳定的温度范围来稳定蛋白质。我们的结果还阐明了相互作用的分子机制，并验证了当前对冷变性机制的理论解释。
