Structure and Function of a Bacterial Na Channel

描述（由申请人提供）：离子通道控制思维大脑、跳动心脏、收缩肌肉和身体每个细胞的活动。它们是许多治疗剂的靶点；离子通道基因的突变是几十种遗传性疾病的原因，包括心律失常和神经系统疾病。许多离子通道随着细胞膜上电压的变化而打开。本提案的中心长期目标是了解离子通道电压门控的分子机制。我们最近在细菌中发现了一种离子通道（NaChBac），它具有人类一类重要离子通道的许多特性：它选择性地渗透到钠中，通过膜电压的变化打开（门控），并在电压依赖性门控后以时间依赖性的方式失活。NaChBac是唯一一个可以在哺乳动物细胞系中表达和研究的电压依赖性离子通道。这一点很重要，因为细菌通道是高分辨率结构研究（x射线晶体学）中最可能获得足够蛋白质的来源。NaChBac蛋白已经结晶，可能产生高分辨率的结构数据。因此，通过诱变和电生理研究的结合来研究这种离子通道的结构和功能是至关重要的。获得的有关离子选择性、电压门控和失活的信息可以直接与结构相关。了解这种相对简单的离子通道将有助于我们了解更大类的离子通道是如何起作用的，并最终帮助我们用治疗药物靶向它们。

DESCRIPTION (provided by applicant): Ion channels govern the activity of the thinking brain, beating heart, contracting muscle, and every cell of the body. They are targets of many therapeutic agents; mutations of ion channel genes are the cause of dozens of inherited diseases, including cardiac arrhythmias and neurological illnesses. Many of these ion channels are opened in response to changes in voltage across the cell membrane. The central long-term aim of this proposal is to understand the molecular mechanism of voltage gating of ion channels. We recently discovered an ion channel in bacteria (NaChBac) that has many of the properties of an important class of ion channels in humans: it is selectively permeant to sodium, opened (gated) by changes in membrane voltage, and inactivated in a time-dependant manner after voltage-dependant gating.NaChBac is unique in being the only voltage-dependent ion channel that can be expressed and studied in a mammalian cell line. This is important because bacterial channels are the most likely sources of sufficient protein for high-resolution structural studies (X-ray crystallography). The NaChBac protein has been crystallized and is likely to yield high-resolution structural data. It is thus crucial to investigate the structure and function of this ion channel through a combination of mutagenic and electrophysiologic studies. Information gained about its ion selectivity, voltage gating, and inactivation can then be directly correlated to the structure when obtained. Understanding this relatively simple ion channel will help us understand how the larger class of channels function, and eventually how we might target them with therapeutic agents.