Thermodynamic Analysis of Protein Stability

了解蛋白质的第三种结构是如何在其氨基酸序列中编码的，这是现代生命科学研究中的主要目标之一。好吧，这个目标还没有实现。原因之一是，蛋白质结构并不只是由氨基酸序列的一部分构成，但也是由更广泛的相互作用构成的。在事实上，同样的特性在规范性稳定性中带来了不同的变化。这些结果显示了一种氨基酸替代对蛋白质稳定性的影响，取决于突变位点的位置及其在蛋白质结构中的环境。如果要估计每一个因素对蛋白质稳定性的贡献，那么结构和稳定性变化的数据必须通过研究许多具有系统性和综合性替代品的突变蛋白来扩展。在这个项目中，我们试图估计一些因素有助于使用一个蛋白质来实现数据库稳定性的一致性，从一系列的突变人类合成酶中获得。因此，我们构建了超过100种不同的人类合成酶。通过DSC和X射线分析评估的稳定性和结构的变化，尊重地。使用结构和稳定性变化的数据库，在这个项目中发现了哪些变化，碳原子的氢磷酸程度（C），以及氮和中性氧原子的氢磷酸程度（N/O）可以估计为0.178 kJ/mol/[0.013 kJ/mol/[0.013 kJ/mol/[0.012] D1，尊重。一种内分子氢键、一种蛋白质和有序水分子之间的内分子键和一种有序水分子之间的内分子键的净贡献估计为8.5、5.2和5.0千焦/摩尔，相应地，为一种长度为3焦耳的氢键。对水分子的引入的入口成本估计也可能达到约8千焦/摩尔。

Understanding how tertiary structures of proteins are coded for in their amino acid sequences is one of the main targets in modern life science research. However, this goal has not yet been achieved. One of the reasons is that a protein structure is prescribed not only by a part of the amino acid sequence but also by an extensive interaction. In fact, the same kinds of substitutions give different changes in conformational stability. These results show that the effect of a single amino acid substitution on protein stability depends on the location of the mutation site and its environment in the protein structure. In order to estimate the contribution of each factor to protein stability, the data of structure and stability changes must be expanded by studying many mutant proteins with systematic and comprehensive substitutions. In this project, we tried to estimate some factors that contribute to conformational stability of a protein using data base of stability/structure, which are obtained from a series of mutant human lysozymes. Then, we constructed more than 100 mutant human lysozymes. Changes in stabilities and structures due to mutations were evaluated by DSC and X-ray analysis, respectively. Using database of structure and stability changes due to mutations, which are obtained in this project, the magnitude of hydrophobicity of carbon atom (C), and the hydrophobicity of nitrogen and neutral oxygen atoms (N/O) could be estimated to be 0.178 kJ/mol/ÅィイD12ィエD1, and -0.013 kJ/mol/ÅィイD12ィエD1, respectively. The net contribution of an intramolecular hydrogen bond, an intermolecular one between protein and ordered water molecules, and an intermolecular one between ordered water molecules was estimated to be 8.5, 5.2, and 5.0 kJ/mol, respectively, for a hydrogen bond with 3 Å length. The entropic cost due to the introduction of a water molecule could be also estimated to be about 8 kJ/mol.