Ionic competition in protein-nucleic acid interactions

凭借该奖项，加尔维斯顿德克萨斯大学医学分支（UTMB）的Junji Iwahara博士获得了研究蛋白质和核酸离子相互作用的支持。这些蛋白质和核酸形成离子对，其涉及带正电荷的基团和带负电荷的基团之间的强静电相互作用。离子对对于生物分子功能是重要的;然而，尚不清楚大分子离子对如何受到溶液中自由离子的影响。该项目小组正在使用基于光的方法（核磁共振（NMR）光谱）来研究蛋白质-DNA界面上自由离子和大分子离子对之间的相互作用。 由于离子对对于许多特定的分子缔合过程是重要的，因此对分子界面处的离子对的更深入的了解促进了农业、制药和生物技术工业中合成化合物的开发。 该项目使高中生能够在研究者的实验室中参与跨学科的研究。 图尔斯的核磁共振设施提供给所有高中学生在UTMB的夏季研究计划。该研究项目的总体目标是了解生物系统中原子水平上自由离子和大分子离子对之间的竞争。特别是，该项目旨在了解离子竞争与蛋白质-核酸复合物分子性质的关系。在形成分子间离子对时，蛋白质侧链和DNA磷酸基团的带电部分与溶液中的游离阳离子（例如钾离子）和阴离子（例如氯离子）竞争。该研究小组正在研究同源结构域DNA结合蛋白HoxD 9和MeCP 2的甲基-CpG结合结构域的DNA复合物中分子界面的离子竞争。NMR光谱用于在原子水平上研究离子竞争的影响。采用等温滴定量热法和停流荧光光谱法从分子水平研究了离子竞争对配合物热力学和动力学性质的影响。本研究项目是将生物物理学方法与诱变技术相结合，以阐明离子竞争及其在蛋白质-核酸相互作用中的作用，本研究项目由化学系生命过程化学项目和分子与细胞生物科学系分子生物物理学组联合资助。

With this award, Dr. Junji Iwahara from University of Texas Medical Branch (UTMB) at Galveston is supported to investigate ionic interactions of proteins and nucleic acids. These proteins and nucleic acids form ion pairs that involve strong electrostatic interactions between positively and negatively charged groups. Ion pairs are important for biological molecular functions; however, it is not well understood how the macromolecular ion pairs are influenced by free ions in solution. The project team is using light-based methods (nuclear magnetic resonance (NMR) spectroscopy) to study the interplay between free ions and macromolecular ion pairs at protein-DNA interfaces. Because ion pairs are important for many specific molecular association processes, deeper knowledge of the ion pairs at molecular interfaces facilitate development of synthetic compounds in the agricultural, pharmaceutical, and biotechnological industries. This project enables high school students to participate in the interdisciplinary research in the investigator's laboratory. Tours of the NMR facilities are offered to all high school students in UTMB's summer research program. The overall goal in this research project is to understand competition between free ions and macromolecular ion pairs at an atomic level in a biological system. In particular, the project aims at understanding the relationship of the ionic competition to the molecular properties of protein-nucleic acid complexes. In forming intermolecular ion pairs, the charged moieties of protein side-chains and DNA phosphate groups compete with free cations (e.g. potassium ions) and anions (e.g. chloride ions) in solution. The research team is studying the ionic competition at molecular interfaces in the DNA complexes of the homeodomain DNA binding protein HoxD9 and the methyl-CpG-binding domain of MeCP2. NMR spectroscopy is used to study the influence of ionic competition at an atomic level. Isothermal titration calorimetry and stopped-flow fluorescence spectroscopy are used to study the influence of ionic competition on the thermodynamic and kinetic properties of the complexes at a molecular level. This research project is integrating biophysical methods with mutagenesis, to delineate the ionic competition and its role in the protein-nucleic acid interactions.This project is jointly funded by the Chemistry of Life Processes Program in the Division of Chemistry and the Molecular Biophysics Cluster in the Division of Molecular and Cellular Biosciences.