Molecular Mechanisms of Caton Channel Selectivity

描述（由申请人提供）：离子通道是控制离子（如K+、Na+、Ca 2+和Cl-）跨细胞膜流动的膜蛋白。它们调节许多生物过程，如神经和肌肉细胞的兴奋，激素的分泌和感觉传导。在人类中，它们几乎存在于所有组织中，执行各种任务。由于它们在人体中的普遍性和重要性，离子通道功能障碍通常是各种人类病理学的核心。离子选择性，即通道仅允许特定离子通过其孔而排除所有其他离子，是定义离子通道的特征性质之一。了解这一过程是获得有关通道相关生物活动和疾病的基础知识的核心。尽管在过去的五年里，在理解K+选择性方面取得了巨大的进展，特别是对几个K+通道的结构测定，但对于任何其他阳离子通道，几乎没有结构信息。更具体地说，我的实验室将专注于研究两组阳离子通道的选择性：非特异性阳离子通道，使用来自蜡状芽孢杆菌的NaK通道作为模型系统，该通道是一种与CNG通道的孔同源的细菌Na+和K+传导通道;以及原核细胞电压门控Na+通道。我们将使用晶体学和电生理学工具的组合来表征这些通道的结构和功能。拟议的研究有三个具体目标。第一个具体目标是在钠钾通道的单价阳离子传导的结构和功能研究。这项研究将使我们能够阐明NaK离子渗透性的分子机制，也将为理解CNG通道家族中离子选择性的结构基础提供重要的见解。我们的第二个具体目标是研究NaK通道的二价阳离子阻断。本研究将阐明CNG通道中二价阳离子阻断的潜在机制，CNG通道是一个具有重要生理意义的过程，特别是对视觉信号转导。第三，我们的目标是确定原核细胞的电压门控Na+通道的离子传导孔的晶体结构。这项研究不仅将使我们能够阐明Na* 通道离子选择性的结构基础，而且还将阐明Ca 2+通道的离子选择性，其选择性过滤器与Na* 通道具有高度的序列同源性。

DESCRIPTION (provided by applicant): Ion channels are membrane proteins that control the flow of ions such as K+, Na+, Ca2+, and CI- across the cell membrane. They regulate many biological processes such as the excitation of nerve and muscle cells, the secretion of hormones, and sensory transduction. In humans, they are found in nearly all tissues serving a variety of tasks. Because of their prevalence and importance in the human body, ion channel dysfunction often lies at the heart of a wide range of human pathologies. Ion selectivity, whereby channels only allow the passage of specific ions through their pores while excluding all others, is one of the characteristic properties defining an ion channel. Understanding this process is central to gaining fundamental knowledge about channel-related biological activities and diseases. Even though tremendous progress has been made over the last five years in understanding K+ selectivity, especially with the structure determination of several K+ channels, there is little structural information available for any other cation channels The overall goal of my research is to understand the structural basis of cation channel selectivity. More specifically, my laboratory will focus on studying the selectivity of two groups of cation channels: non specific cation channels, using the NaK channel from Bacillus cereus, a bacterial Na+ and K+ conducting channel that is homologous to the pore of a CNG channel, as a model system; and the prokaryotic voltage- gated Na+ channels. We will use a combination of crystallographic and electrophysiological tools to characterize these channels both structurally and functionally. The proposed research has three specific aims. The first specific aim is the structural and functional study of monovalent cation conduction in the NaK channel. This study will allow us to elucidate the molecular mechanisms underlying ion permeability in NaK, and will also provide crucial insights into understanding the structural basis of ion selectivity in the CNG channel family. Our second specific aim is to study the divalent cation blockage of the NaK channel. This study will elucidate the underlying mechanism of divalent cation blockage in CNG channels, a process of crucial physiological significance, especially to visual transduction. Third, we aim to determine the crystal structure of the ion conduction pore of a prokaryotic voltage-gated Na+ channel. This study will not only allow us to elucidate the structural basis of ion selectivity in Na* channels, but will also shed light on the ion selectivity of Ca2+ channels whose selectivity filter shares high sequence homology to that of Na* channels.