Increasing the net charge and decreasing the hydrophobicity of bovine carbonic anhydrase decreases the rate of denaturation with sodium dodecyl sulfate
Increasing the net charge and decreasing the hydrophobicity of bovine carbonic anhydrase decreases the rate of denaturation with sodium dodecyl sulfate
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DOI：
10.1529/biophysj.106.081547
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发表时间：
2006-07-01
影响因子：
3.4
通讯作者：
Whitesides, George M.
中科院分区：
文献类型：
--
作者：
Gudiksen, Katherine L.;Gitlin, Irina;Whitesides, George M.
本研究比较了牛碳酸酐酶II （BCA）赖氨酸epsilon-NH3+基酰化产生的蛋白质电荷阶梯的单个梯级与十二烷基硫酸钠（SDS）的变性速率。每一次酰化都会减少带正电的基团数量，增加净负电荷，增加BCA的疏水表面积。本研究报道了醋酸酐和己酸酐生成的蛋白质电荷梯在含有SDS的溶液中的变性动力学；将这些变性率绘制为莫迪数的函数。阳离子产生u型曲线。具有中间数目的莫迪的蛋白质。阳离子对SDS变性最稳定。有四种相互竞争的相互作用——两种是由静电的变化引起的，另两种是由暴露的疏水表面积的变化引起的——决定了a如何变化。阳离子影响BCA电荷阶梯一级对SDS变性的稳定性。基于这些相互作用如何影响折叠态和跃迁态的假设，已经建立了一个模型，并与实验结果吻合。模拟表明，每增加一个酰化，变性活化能（Delta Delta Gz）因静电变化而变化的幅度远大于因疏水性变化而变化的DDGz，但分子间和分子内静电效应的符号相反。在高数量的酰化时，疏水相互作用导致己醇修饰的BCA变性速度比乙酰修饰的BCA快近三个数量级。
This study compares the rate of denaturation with sodium dodecyl sulfate (SDS) of the individual rungs of protein charge ladders generated by acylation of the lysine epsilon-NH3+ groups of bovine carbonic anhydrase II (BCA). Each acylation decreases the number of positively charged groups, increases the net negative charge, and increases the hydrophobic surface area of BCA. This study reports the kinetics of denaturation in solutions containing SDS of the protein charge ladders generated with acetic and hexanoic anhydrides; plotting these rates of denaturation as a function of the number of modi. cations yields a U-shaped curve. The proteins with an intermediate number of modi. cations are the most stable to denaturation by SDS. There are four competing interactions-two resulting from the change in electrostatics and two resulting from the change in exposed hydrophobic surface area-that determine how a modi. cation affects the stability of a rung of a charge ladder of BCA to denaturation with SDS. A model based on assumptions about how these interactions affect the folded and transition states has been developed and fits the experimental results. Modeling indicates that for each additional acylation, the magnitude of the change in the activation energy of denaturation (Delta Delta Gz) due to changes in the electrostatics is much larger than the change in DDGz due to changes in the hydrophobicity, but the intermolecular and intramolecular electrostatic effects are opposite in sign. At the high numbers of acylations, hydrophobic interactions cause the hexanoyl-modified BCA to denature nearly three orders of magnitude more rapidly than the acetyl-modified BCA.