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首页> 外文期刊>Biochemistry >Changes in Stability upon Charge Reversal and Neutralization Subtitution in Staphylococcal Nuclease Are Dominated by Favorable Electrostatic Effects
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Changes in Stability upon Charge Reversal and Neutralization Subtitution in Staphylococcal Nuclease Are Dominated by Favorable Electrostatic Effects

机译：葡萄球菌核酸酶中电荷反转和中和取代后的稳定性变化受静电作用的支配。

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摘要

Single site mutations that reverse or neutralize a surface charge were made at 22 ionizable residues in staphylococcal nuclease. Unfolding free energies were obtained by guanidine hydrochloride denaturation. These data, in conjunction with previously obtained stabilities of the corresponding alanine mutants, unequivocall show that the dominant contribution to stability of the corresponding alanine mutants, unequivocally show that the dominant contribution to stability for virtually all of the wild-type side chains examined is the electrostatic effect associated with each residue's charged group. With only a few exceptions, these charges stabilize the native state, with an average loss of 0.5 kcal/mol of stability upon neutralization of a charge. When the charge is reversed, the average destabilization is doubled. Structure-based calculations of electrostatic free energy with the continum method based on the finite difference solution to the lineaized Poisson-Boltzmann equation reproduce the observed energetics when the polarizability in the protein interior is represented with a dielectric constant of 20. However, in some cases, large differences are found, giving insight into possible areas for improvement of the calculations. In particular, it appears that the assumptions made in the calculations about the absence of electriostatic interactions in the denaturated state and the energetic consequences of dynamic fluctuations in the native state will have to be further explored.
机译：在葡萄球菌核酸酶中的22个可电离的残基上进行了可逆或中和表面电荷的单点突变。通过盐酸胍变性获得展开的自由能。这些数据与先前获得的相应丙氨酸突变体的稳定性相结合，明确表明，对相应丙氨酸突变体的稳定性起主要作用，明确表明实际上对所有检测到的野生型侧链的稳定性起主要作用。与每个残基带电基团相关的静电效应。除少数例外，这些电荷稳定了原始状态，电荷中和后平均损失了0.5 kcal / mol的稳定性。当电荷反转时，平均不稳定度增加一倍。基于线性化Poisson-Boltzmann方程的有限差分解的基于连续方法的基于结构的静电自由能计算，当蛋白质内部的极化率以20的介电常数表示时，可再现观察到的能量。 ，发现差异很大，从而深入了解了可能需要改进的计算领域。特别地，似乎在计算中做出的关于在变性状态下不存在静电相互作用以及在原始状态下动态波动的能量后果的假设将需要进一步探索。

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