PROTEIN DENATURATION WITH GUANIDINE-HYDROCHLORIDE OR UREA PROVIDES A DIFFERENT ESTIMATE OF STABILITY DEPENDING ON THE CONTRIBUTIONS OF ELECTROSTATIC INTERACTIONS
PROTEIN DENATURATION WITH GUANIDINE-HYDROCHLORIDE OR UREA PROVIDES A DIFFERENT ESTIMATE OF STABILITY DEPENDING ON THE CONTRIBUTIONS OF ELECTROSTATIC INTERACTIONS
复制标题
DOI：
10.1002/pro.5560031110
复制
发表时间：
1994-11-01
期刊：
影响因子：
8
通讯作者：
HODGES, RS
中科院分区：
文献类型：
--
作者：
MONERA, OD;KAY, CM;HODGES, RS
本研究的目的是探讨尿素和盐酸胍（GdnHCl）对某一特定蛋白质稳定性的评估是否相同。我们先前怀疑，从GdnHCl和尿素变性数据得出的蛋白质稳定性评估可能因稳定蛋白质的静电相互作用而有所不同。因此，设计了4种卷曲螺旋类似物，其中链内和链间静电吸引力（A）的数量被系统地改变为排斥力（R）：20A、15A5R、10A10R和20R。GdnHCl变性数据显示，这4种具有从20个吸引力到20个排斥力的静电相互作用的卷曲螺旋类似物，具有非常相似的[GdnHCl]₁/₂值（平均值约为3.5 M），并且它们的ΔΔG(u)值也非常接近0（0.2千卡/摩尔）。相比之下，尿素变性显示[尿素]₁/₂值随着从20个静电吸引力到20个排斥力的逐步变化而成比例地降低（20A，7.4 M；15A5R，5.4 M；10A10R，3.2 M；20R，1.4 M），并且ΔΔG(u)值随着静电相互作用差异的增加而相应增加（20A - 15A5R，1.5千卡/摩尔；20A - 10A10R，3.7千卡/摩尔；20A - 20R，5.8千卡/摩尔）。这些结果表明，GdnHCl的离子性质掩盖了这些模型蛋白质中的静电相互作用，而在使用不带电荷的尿素时则没有这种现象。因此，根据静电相互作用对蛋白质的重要性，GdnHCl和尿素变性可能对蛋白质稳定性给出非常不同的评估。
The objective of this study was to address the question of whether or not urea and guanidine hydrochloride (GdnHCl) give the same estimates of the stability of a particular protein. We previously suspected that the estimates of protein stability from GdnHCl and urea denaturation data might differ depending on the electrostatic interactions stabilizing the proteins. Therefore, 4 coiled-coil analogs were designed, where the number of intrachain and interchain electrostatic attractions (A) were systematically changed to repulsions (R): 20A, 15A5R, 10A10R, and 20R. The GdnHCl denaturation data showed that the 4 coiled-coil analogs, which had electrostatic interactions ranging from 20 attractions to 20 repulsions, had very similar [GdnHCl](1/2) values (average of similar or equal to 3.5 M) and, as well, their Delta Delta G(u) values were very close to 0 (0.2 kcal/mol). In contrast, urea denaturation showed that the [urea](1/2) values proportionately decreased with the stepwise change from 20 electrostatic attractions to 20 repulsions (20A, 7.4 M; 15A5R, 5.4 M; 10A10R, 3.2 M; and 20R, 1.4 M), and the Delta Delta G(u) values correspondingly increased with the increasing differences in electrostatic interactions (20A - 15A5R, 1.5 kcal/mol; 20A - 10A10R, 3.7 kcal/mol; and 20A - 20R, 5.8 kcal/mol). These results indicate that the ionic nature of GdnHCl masks electrostatic interactions in these model proteins, a phenomenon that was absent when the uncharged urea was used. Thus, GdnHCl and urea denaturations may give vastly different estimates of protein stability, depending on how important electrostatic interactions are to the protein.