Ion-selectivity and mechanisms of the Na/K pump

细胞膜上的离子（带电原子或分子）浓度存在很大差异，细胞膜将细胞与环境隔开。这种浓度差用于驱动许多基本的细胞过程，并且它由许多膜泵建立和维持，这些膜泵是负责将这些离子转运穿过膜的蛋白质。该项目将吸引本科生（包括在科学中代表性不足的少数民族成员）和研究生参与特定膜泵选择和跨膜输送钠和钾离子的基本特性的调查。除了生物物理技术培训外，还将支持学生参加国家科学会议，他们将能够在会上介绍他们的研究成果。Na/K泵是产电的，因为它在每个催化循环中将3个Na+运出细胞，以换取2个K+。三个位点中的一个可以专门结合Na+（这是Na/K泵与其他P型ATP酶的区别）。所有的P型ATP酶都在两种主要构象之间交替，E1具有向内的离子结合位点，E2具有向外的离子结合位点。Na/K泵的离子选择性的分子机制仍不清楚，但这些知识对于理解这些蛋白质如何将ATP水解的化学能与离子移位所需的机械功耦合至关重要。该项目将研究Na/K泵中离子选择的机制，采用创新的方法，将高时间分辨率的电生理学，计算化学和生物化学相结合。现有的晶体结构和我们实验室的结果将被用来产生关于以下方面的假设：（a）阐明两种主要泵构象中的离子选择性机制;（B）确定细胞内Na+结合和外部Na+释放的顺序;和（c）识别通过Na/K泵的非偶联H+流入的途径和机制。

Cells maintain large differences in the concentration of ions (electrically charged atoms or molecules) across the membrane that separates the cell from its environment. This concentration difference is used to drive many essential cellular processes and it is established and maintained by numerous membrane pumps, which are proteins responsible for transporting these ions across the membrane. This project will engage undergraduate students (including members of minorities underrepresented in science) and graduate students in investigations of the fundamental properties by which a particular membrane pump selects and transports sodium and potassium ions across membranes. In addition to training in biophysical techniques, the students will be supported to attend national scientific meetings at which they will be able to present the results of their research.The Na/K pump is electrogenic because it transports 3 Na+ out of the cell in exchange for 2 K+, in each catalytic cycle. One out of three sites can exclusively bind Na+ (a feature that distinguishes the Na/K pump from other P-type ATPases). All P-type ATPases alternate between two major conformations, E1 with inward facing ion binding sites and E2 with outward facing ion binding sites. The molecular mechanisms of ion selectivity by the Na/K pump remain unclear, yet knowledge of these is critical to an understanding of how these proteins couple the chemical energy of ATP hydrolysis to the mechanical work required for ion translocation. This project will study the mechanisms of ion selection in the Na/K pump with an innovative approach that integrates high-temporal-resolution electrophysiology, computational chemistry and biochemistry. The available crystal structures and results from our laboratory will be used to generate hypotheses with respect to (a) Elucidating the mechanisms of ion selectivity in the two major pump conformations; (b) Determining the order of intracellular Na+ binding and external Na+ release; and (c) Identifying the pathway and mechanisms of uncoupled H+ influx through Na/K pumps.