Conformational Stability of Globular Proteins

描述（由申请人提供）：现在可以用任何氨基酸序列构建蛋白质。这项技术在卫生和其他领域应用的重要性现在已经很清楚，而且主要受到我们目前的知识和想象力的限制。因此，我们必须学会预测氨基酸序列的变化将如何影响蛋白质的化学和物理性质、功能、折叠和稳定性。这里提出的研究将导致更好地理解：1)促进蛋白质稳定性的力量；2)决定蛋白质可电离基团pK值的相互作用；3)单个侧链对蛋白质溶解度的贡献。我们将研究核糖核酸酶Sa的Thr到Val和Val到Thr突变体的折叠热力学。这些结果将使我们能够评估埋入极性-OH基团或非极性-CH - 3基团是否会使蛋白质获得更多的稳定性，并将为我们提供有关稳定蛋白质的力的基本信息。这些结果将有助于理论化学家改进用于预测和增强蛋白质结构的方法。在一个相关的项目中，我们将研究极极性但不溶于水的肽GNNQQNY的溶解热力学，GNNQQNY在固体状态下以平行的β -片为广泛的氢键。这一过程将作为蛋白质展开时极性基团暴露于溶剂的模型，并将提高我们对几种疾病中形成的淀粉样斑块的理解。蛋白质中单个可电离残基的pK值主要取决于Born自能、氢键和电荷-电荷相互作用。为了评估Born自能对pK值的贡献，我们将测量引入RNase Sa的埋藏电离基团的pK值。为了评估氢键对pK的贡献，我们将测量RNase T1中Asp 76 （pK = 0.5）和RNase Sa中Asp 33 （pK = 2.3）的pK值的变化，因为它们的氢键伴侣被移除。为了更好地了解蛋白质的溶解度，我们将研究RNase Sa氨基酸序列的单一变化对蛋白质折叠和未折叠状态溶解度的影响。

DESCRIPTION (provided by applicant): Proteins can now be constructed with any amino acid sequence. The importance of applications of this technology in health and other areas is now clear and limited mostly by our current knowledge and imagination. Thus, it is essential that we learn to predict how changes in the amino acid sequence will affect the chemical and physical properties, the function, the folding, and the stability of a protein. The research proposed here will lead to a better understanding of 1) the forces contributing to protein stability; 2) the interactions that determine the pK values of the ionizable groups of proteins; and 3) the contribution of individual side chains to protein solubility. We will study the thermodynamics of folding of Thr to Val and Val to Thr mutants of ribonuclease Sa. These results should allow us to assess whether proteins gain more stability from burying polar -OH groups or nonpolar -CH 3 groups and will provide us with fundamental information on the forces stabilizing proteins. These results should help theoretical chemists improve the methods used to predict and enhance protein structure. In a related project, we will study the thermodynamics of dissolution of the very polar but water insoluble peptide, GNNQQNY, which is extensively hydrogen bonded in a parallel beta-sheet in the solid state. This process will serve as a model for the exposure of polar groups to solvent when a protein unfolds, and will improve our understanding of the amyloid plaques that form in several diseases. The pK values of individual ionizable residues in a protein depend mainly on the Born self energy, hydrogen bonding, and charge-charge interactions. To assess the contribution of the Born self energy to the pK values, we will measure the pK values of buried ionizable groups introduced into RNase Sa. To assess the contribution of hydrogen bonding to pKs, we will measure the changes in the pK values of Asp 76 (pK = 0.5) in RNase T1 and.Asp 33 (pK = 2.3) in RNase Sa as their hydrogen bonding partners are removed. To gain a better understanding of protein solubility, we will study the effect of single changes in the amino acid sequence of RNase Sa on the solubility of the folded and unfolded states of the protein.