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+、Ca2+和CI-在细胞膜上流动的膜蛋白。它们调节许多生物过程，如神经和肌肉细胞的兴奋、激素的分泌和感觉转导。在人类中，它们几乎存在于所有组织中，承担着各种各样的任务。由于其在人体中的普遍性和重要性，离子通道功能障碍往往是一系列人类病理的核心。离子的选择性，即通道只允许特定的离子通过它们的孔，而不允许所有其他的，是定义离子通道的特征性质之一。了解这一过程对于获得与通道相关的生物活动和疾病的基本知识至关重要。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，特别是在几个K+通道的结构确定方面，但是对于任何其他阳离子通道的结构信息很少。我的研究的总体目标是了解阳离子通道选择性的结构基础。更具体地说，我的实验室将重点研究两组阳离子通道的选择性：非特异性阳离子通道，使用蜡样芽孢杆菌的NaK通道作为模型系统，这是一种与CNG通道孔同源的细菌Na+和K+传导通道；以及原核生物电压门控的Na+通道。我们将结合晶体学和电生理工具来描述这些通道的结构和功能。拟议的研究有三个具体目标。第一个具体目标是研究NaK通道中单价阳离子传导的结构和功能。这项研究将使我们能够阐明NaK中离子渗透的分子机制，并将为理解CNG通道家族中离子选择性的结构基础提供重要见解。我们的第二个具体目标是研究二价阳离子对NaK通道的阻断。本研究将阐明二价阳离子阻断CNG通道的潜在机制，这是一个具有重要生理意义的过程，特别是对视觉转导。第三，我们的目标是确定原核电压门控Na+通道离子传导孔的晶体结构。该研究不仅可以阐明Na*通道中离子选择性的结构基础，还可以揭示与Na*通道具有高度序列同源性的Ca2+通道的离子选择性。

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.