Ionic competition in protein-nucleic acid interactions

来自加尔维斯顿德克萨斯大学医学分部（UTMB）的Junji Iwahara博士获得了该奖项，支持他研究蛋白质和核酸的离子相互作用。这些蛋白质和核酸形成离子对，在带正电荷和带负电荷的基团之间形成强静电相互作用。离子对是生物分子功能的重要组成部分；然而，溶液中自由离子对大分子离子对的影响尚不清楚。该项目团队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。由于离子对在许多特定的分子结合过程中很重要，对分子界面离子对的深入了解有助于农业、制药和生物技术行业合成化合物的开发。该项目使高中生能够参与研究者实验室的跨学科研究。核磁共振设施的旅游是提供给所有高中学生在UTMB的夏季研究计划。本研究项目的总体目标是在原子水平上了解生物系统中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-核酸复合物分子特性的关系。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自由阳离子（如钾离子）和阴离子（如氯离子）竞争。研究小组正在研究同源结构域DNA结合蛋白HoxD9和MeCP2甲基- cpg结合结构域DNA复合物分子界面上的离子竞争。核磁共振波谱用于研究离子竞争在原子水平上的影响。采用等温滴定量热法和停止流动荧光光谱法在分子水平上研究了离子竞争对配合物热力学和动力学性质的影响。本研究项目将生物物理方法与诱变相结合，描述离子竞争及其在蛋白质-核酸相互作用中的作用。本项目由化学学部生命过程化学项目和分子与细胞生物科学部分子生物物理集群共同资助。

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.