Ionic selectivity and thermal adaptations within the voltage-gated sodium channel family of alkaliphilic Bacillus.
Ionic selectivity and thermal adaptations within the voltage-gated sodium channel family of alkaliphilic Bacillus.
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DOI：
10.7554/elife.04387
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发表时间：
2014-11-11
期刊：
影响因子：
7.7
通讯作者：
Clapham DE
中科院分区：
文献类型：
--
作者：
DeCaen PG;Takahashi Y;Krulwich TA;Ito M;Clapham DE
阳离子的进入和排出是活细胞中必不可少的过程。在嗜碱原核生物中，高外部pH激活电压门控钠通道（Nav），其允许Na+进入并用作负责细胞质pH稳态的阳离子/质子反向转运蛋白的底物。在这里，我们描述了一个新的成员的原核电压门控Na+通道家族（NsvBa;非选择性电压门控，嗜碱芽孢杆菌），是非选择性的Na+，Ca 2+和K+离子。NsvBa的突变可以将非选择性过滤器转换为区分Na+或二价阳离子的过滤器。功能获得实验证明了具有过滤器突变的离子选择性对其他芽孢杆菌Nav通道的可移植性。增加pH和温度使其活化阈值向其天然静息膜电位移动。此外，我们发现靶向芽孢杆菌Nav通道的药物也可以阻止细菌的生长。这项工作确定了一些适应，以实现离子歧视和门控芽孢杆菌Nav通道。DOI：http://dx.doi.org/10.7554/eLife.04387.001生命本质上是靠电运行的：电信号引起神经细胞放电，心肌收缩，使生物体能够感知周围的世界。这些信号是由带正电荷的离子（如钠、钾和钙）通过细胞膜中的特殊离子通道进入细胞的运动触发的，这些离子通道可以响应细胞膜上电压的变化而打开和关闭。除了少数例外，电压敏感离子通道通常只允许一种类型的离子进入细胞。但是离子通道是如何区分不同的离子的，它们又是如何在进化过程中获得这种能力的呢？为了解决这些问题，研究人员在过去十年中研究了细菌的一个钠通道家族。DeCaen等人在这里描述了一个来自这个离子通道家族的新成员，它来自一种叫做嗜碱芽孢杆菌的细菌。该离子通道不能区分带正电荷的离子和B。嗜碱菌需要这种离子通道，以便在钾或钠含量高的环境中生存。DeCaen等人证明，这些离子通道可以对钠或钙具有选择性，只需在编码离子通道的基因中进行两个小的改变。此外，在来自其他芽孢杆菌属物种的相关离子通道基因中进行类似的基因突变具有相同的效果。DeCaen等人提出，芽孢杆菌属离子通道基因容易适应于在具有不同水平的正电荷离子的各种环境条件下发挥功能。因此，芽孢杆菌通道更容易进化为对不同离子具有选择性。芽孢杆菌属细菌在温热温度和碱性pH下迅速分裂。DeCaen等人证明，这两种条件都使芽孢杆菌属离子通道更容易响应电压而打开。此外，DeCaen等人证明，芽孢杆菌离子通道可以被损害细菌生长能力的药物靶向。这些发现，以及其他揭示药物分子与离子通道结合的工作，可能会指导开发其他芽孢杆菌菌株引起的疾病的治疗方法，包括炭疽和某些形式的食物中毒。DOI：http://dx.doi.org/10.7554/eLife.04387.002网站
Entry and extrusion of cations are essential processes in living cells. In alkaliphilic prokaryotes, high external pH activates voltage-gated sodium channels (Nav), which allows Na+ to enter and be used as substrate for cation/proton antiporters responsible for cytoplasmic pH homeostasis. Here, we describe a new member of the prokaryotic voltage-gated Na+ channel family (NsvBa; Non-selective voltage-gated, Bacillus alcalophilus) that is nonselective among Na+, Ca2+ and K+ ions. Mutations in NsvBa can convert the nonselective filter into one that discriminates for Na+ or divalent cations. Gain-of-function experiments demonstrate the portability of ion selectivity with filter mutations to other Bacillus Nav channels. Increasing pH and temperature shifts their activation threshold towards their native resting membrane potential. Furthermore, we find drugs that target Bacillus Nav channels also block the growth of the bacteria. This work identifies some of the adaptations to achieve ion discrimination and gating in Bacillus Nav channels. DOI: http://dx.doi.org/10.7554/eLife.04387.001 Life essentially runs on electricity: electrical signals cause nerve cells to fire, heart muscles to contract and allow organisms to sense the world around them. These signals are triggered by the movement of positively-charged ions—such as sodium, potassium and calcium—moving into a cell through special ion channels in the cell membrane, which can open and close in response to changes in the voltage across the cell membrane. With few exceptions, voltage sensitive ion channels usually only let one type of ion pass into the cell. But how do ion channels discriminate amongst ions and how did they acquire this ability during evolution? To address these questions, researchers have studied a family of sodium channels from bacteria for the past decade. Here DeCaen et al. describe a new member from this ion channel family from a bacterium called Bacillus alcalophilus. This ion channel does not discriminate between positively-charged ions and B. alcalophilus needs this ion channel for it to dwell in environments that have high levels of potassium or sodium. DeCaen et al. demonstrate that these ion channels can be made selective for sodium or calcium with as little as two small changes in the gene that encodes the ion channel. Furthermore, making similar genetic mutations in related ion channel genes from other Bacillus species has the same effect. DeCaen et al. suggest that Bacillus ion channel genes are easily adapted to function in a variety of environmental conditions with different levels of positively-charged ions. Thus it is easier for Bacillus channels to evolve to be selective for different ions. Bacillus bacteria divide rapidly in warm to hot temperatures and under alkaline pH. DeCaen et al. demonstrate that both of these conditions make Bacillus ion channels easier to open in response to voltage. In addition, DeCaen et al. demonstrate that Bacillus ion channels can be targeted by drugs that impair the ability of the bacteria to grow. These findings—together with other work that revealed where drug molecules bind to ion channels—could potentially guide efforts to develop treatments for illnesses caused by other Bacillus strains, which include anthrax and some forms of food poisoning. DOI: http://dx.doi.org/10.7554/eLife.04387.002