Structural Studies on Prokaryotic Potassium Channels

描述（由申请人提供）：离子通道在膜电位、受体电位和动作电位的产生中起重要作用。它们是神经科学中许多细胞的基本特征——兴奋性——的分子基石。这些蛋白与所有可兴奋组织的生理和病理生理有关，是包括癫痫和心律失常在内的许多疾病过程的基础，也是临床医学中使用的基本药物的主要靶点。钾离子通道是一个结构相关的离子通道超家族的系统发育奠基人，包括核苷酸门控通道、钠离子通道和钙离子通道。钾通道通常由四个相同的亚基以四倍对称的方式组装而成。这种相当简单的结构蓝图和只有一种亚基类型的实际优势使钾通道成为一个被广泛研究的模型系统。钾离子通道表现出两个重要的特性：它们选择性地吸收钾而不是钠，它们在一个叫做门控的过程中改变它们的结构。本研究探讨了钾离子通道中的门控转变。我们将结合半胱氨酸扫描诱变、位点定向自旋标记、位点定向质量标记、x射线晶体学和电生理学来研究三个原核钾通道：KcsA、MthK和KvAP的门控转变。本提案的长期目标是在结构水平上了解离子通道的功能特性。

DESCRIPTION (provided by applicant): Ion channels are instrumental in the generation of membrane potential, receptor potential, and action potential. They are the molecular building blocks for what is an essential characteristic of many cells in neuroscience: excitability. These proteins are implicated in the physiology and pathophysiology of all excitable tissues, underlie many disease processes including epilepsies and arrhythmias, and are major targets of essential drugs used in clinical medicine. Potassium channels are the phylogenetic founders of a large superfamily of structurally related ion channels that includes nucleotide gated channels, sodium channels, and calcium channels. Potassium channels are typically assembled from four identical subunits in a four-fold symmetrical fashion. This rather simple structural blueprint and the substantial practical advantage of only one subunit type have made potassium channels a much studied model system. Potassium channels exhibit two important properties: they selectively admit potassium over sodium and they change their structure during function in a process called gating. This proposal explores the gating transition in potassium channels. We will use a combination of cysteine scanning mutagenesis, site-directed spin labeling, site-directed mass tagging, X-ray crystallography, and electrophysiology to study the gating transition in three prokaryotic potassium channels: KcsA, MthK, and KvAP. The long term goal of this proposal is to understand functional properties of ion channels at a structural level.