Salting the charged surface: pH and salt dependence of protein G B1 stability
Salting the charged surface: pH and salt dependence of protein G B1 stability
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DOI：
10.1529/biophysj.105.071050
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发表时间：
2006-04-01
影响因子：
3.4
通讯作者：
Linse, S
中科院分区：
文献类型：
--
作者：
Lindman, S;Xue, WF;Linse, S
这项研究表明蛋白质表面电荷对稳定性有显著影响，这些影响不能通过盐筛选来消除。在低盐、0.15M盐和2M盐的pH-1.5-11范围内，研究了蛋白GB1结构域的一个变异体的稳定性。该变异体有三个突变：T2Q、N8D和N37D，以确保在所有pH值下都有完整的共价链。蛋白质的稳定性表现出明显的pH依赖性，在等电点附近稳定性最高。在所有三种氯化钠浓度下，稳定性都依赖于pH，这表明涉及带电残基的相互作用在所有三种条件下都是重要的。我们发现2M盐在低pH(蛋白质净电荷为+6，总电荷数为6)时对蛋白质有稳定作用，而在高pH(净电荷=18)时则不稳定。此外，0.15M的盐在pH范围内略微降低了蛋白质的稳定性。结果表明，蛋白质的净电荷是不稳定的，这表明蛋白质含有电荷的原因不是为了提高稳定性。在总电荷很少的条件下，盐似乎减少了静电对稳定性的贡献，但在高电荷体系中不能消除静电效应。
This study shows signicant effects of protein surface charges on stability and these effects are not eliminated by salt screening. The stability for a variant of protein G B1 domain was studied in the pH-range of 1.5-11 at low, 0.15 M, and 2 M salt. The variant has three mutations, T2Q, N8D, and N37D, to guarantee an intact covalent chain at all pH values. The stability of the protein shows distinct pH dependence with the highest stability close to the isoelectric point. The stability is pH-dependent at all three NaCl concentrations, indicating that interactions involving charged residues are important at all three conditions. We find that 2 M salt stabilizes the protein at low pH (protein net charge is +6 and total number of charges is 6) but not at high pH (net charge is = 18). Furthermore, 0.15 M salt slightly decreases the stability of the protein over the pH range. The results show that a net charge of the protein is destabilizing and indicate that proteins contain charges for reasons other than improved stability. Salt seems to reduce the electrostatic contributions to stability under conditions with few total charges, but cannot eliminate electrostatic effects in highly charged systems.