Conformational Stability of Globular Proteins

描述(申请人提供)：蛋白质现在可以用任何氨基酸序列构建。这项技术在卫生和其他领域的应用的重要性现在是显而易见的，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。本文提出的研究将有助于更好地理解1)有助于蛋白质稳定性的作用力；2)决定蛋白质可电离基团pk值的相互作用；以及3)单个侧链对蛋白质溶解度的贡献。我们将研究苏氨酸对Val和Val对核糖核酸酶Sa突变体折叠的热力学。这些结果应该使我们能够评估蛋白质是通过掩埋极性-OH基团还是非极性-CH3基团获得更大的稳定性，并将为我们提供关于稳定蛋白质的作用力的基本信息。这些结果应该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多肽GNNQQNY的溶解热力学。GNNQQNY在固体中以平行的β-折叠形式广泛地氢键。这一过程将作为蛋白质展开时将极性基团暴露在溶剂中的模型，并将提高我们对在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值主要取决于固有的自能、氢键和电荷相互作用。为了评估出生的自能对pK值的贡献，我们将测量RNaseSa中引入的掩埋可电离基团的pk值。为了评估氢键对PKS的贡献，我们将测量RNaseT1中Asp 76(Pk=0.5)和RNaseSa中Asp 33(Pk=2.3)的pk值随着它们的氢键伙伴的去除而发生的变化。为了更好地了解蛋白质的溶解性，我们将研究RNaseSa氨基酸序列的单一变化对蛋白质折叠和未折叠状态的溶解度的影响。

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.