Distinct gating mechanisms revealed by the structures of a multi-ligand gated K(+) channel.
Distinct gating mechanisms revealed by the structures of a multi-ligand gated K(+) channel.
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DOI：
10.7554/elife.00184
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发表时间：
2012-12-13
期刊：
影响因子：
7.7
通讯作者：
Jiang Y
中科院分区：
文献类型：
--
作者：
Kong C;Zeng W;Ye S;Chen L;Sauer DB;Lam Y;Derebe MG;Jiang Y
在真核细胞Slo通道家族和大多数配基门控的原核钾通道和转运蛋白中，门控环形成的RCK结构域调节通道门控以响应各种细胞化学刺激。在这里，我们提出了一个双RCK的，多配基门控K+通道的结构和功能的研究，命名为GsuK。我们证明ADP和NAD+激活GsuK通道，而Ca~(2+)起变构抑制作用。多重晶体结构解释了GsuK中多配体门控的结构基础，也揭示了具有节段性内螺旋的独特的离子传导孔。通过结构比较，我们提出了一种不同于其他K+通道的新的开孔机制。DOI：http://dx.doi.org/10.7554/eLife.00184.001大多数细胞都被一层半透膜包围，虽然这层膜允许极少数分子通过，但细胞可以使用跨膜蛋白来克服这一障碍。其中一些蛋白质将葡萄糖、氨基酸和其他营养物质输入细胞，而另一些蛋白质则将离子输送进或运出细胞。离子在细胞膜上的传输对多种生物过程是必不可少的，包括信号转导和神经细胞中产生电脉冲。允许离子通过细胞膜的孔被称为离子通道，大多数通道只允许一种类型的离子-通常是钠、钙或钾(K+)离子-通过它们。有许多不同类型的离子通道，它们根据它们允许通过的离子类型以及用于打开和关闭通道的门控机制进行分类。例如，配体门控的K+通道促进钾离子的通过，并通过与通道的配体结合和解除结合来打开和关闭通道。大多数K+通道由四个相同的亚基组成，在原核生物的大多数配体门控K+通道中，每个亚基都有一个或两个配体结合的RCK结构域(其中RCK代表调节K+的电导)。对于真核生物中的一些K+通道也是如此。虽然已知RCK结构域负责调节钾离子在不同生物细胞膜上的运输，但对由多个配体门控的K+通道的结构或门控机制知之甚少。Kong等人我研究了一种名为GsuK的配体门控K+通道，它的每个亚基有两个RCK结构域，在硫磺还原菌中发现。他们发现，开放过程是由含腺嘌呤的配体(如NAD+或ADP)介导的，而钙离子的存在使该通道关闭。并通过确定多个晶体结构，孔等人。我们能够从结构的角度理解这些配体是如何调节这一通道的，并提出了一种不同于已知的控制其他钾通道的机制的门控机制。DOI：http://dx.doi.org/10.7554/eLife.00184.002
The gating ring-forming RCK domain regulates channel gating in response to various cellular chemical stimuli in eukaryotic Slo channel families and the majority of ligand-gated prokaryotic K+ channels and transporters. Here we present structural and functional studies of a dual RCK-containing, multi-ligand gated K+ channel from Geobacter sulfurreducens, named GsuK. We demonstrate that ADP and NAD+ activate the GsuK channel, whereas Ca2+ serves as an allosteric inhibitor. Multiple crystal structures elucidate the structural basis of multi-ligand gating in GsuK, and also reveal a unique ion conduction pore with segmented inner helices. Structural comparison leads us to propose a novel pore opening mechanics that is distinct from other K+ channels. DOI: http://dx.doi.org/10.7554/eLife.00184.001 Most cells are surrounded by a semipermeable membrane, and although this membrane allows very few molecules to pass through it, cells can use transmembrane proteins to overcome this barrier. Some of these proteins import glucose, amino acids and other nutrients into the cell, while others transport ions into or out of the cell. Ion transport across the cell membrane is essential for a wide variety of biological processes, including signal transduction and the generation of electrical impulses in nerve cells. The pores that allow ions to travel through the cell membrane are known as ion channels, and most channels allow only one type of ion—usually sodium, calcium or potassium (K+) ions—to pass through them. There are many different types of ion channels and they are classified according to the type of ion they allow to pass through them, and by the gating mechanism that is used to open and close the channel. For example, ligand-gated K+ channels facilitate the passage of potassium ions and are opened and closed by ligands binding and unbinding to and from the channel. Most K+ channels are made up of four identical subunits, and in the majority of ligand-gated K+ channels in prokaryotes, each of these subunits will have one or two ligand-binding RCK domains (where RCK stands for regulating the conductance of K+). This is also true for some K+ channels in eukaryotes. While it is known that RCK domains are responsible for regulating the transport of potassium ions across the cell membranes of diverse organisms, little is known about the structure or gating mechanisms of K+ channels that are gated by more than one ligand. Kong et al. have studied a ligand-gated K+ channel called GsuK that has two RCK domains per subunit and is found in the bacterium G. sulfurreducens. They found that the opening process was mediated by a ligand that contains adenine, such as NAD+ or ADP, and the channel was closed by the presence of calcium ions. And by determining multiple crystal structures, Kong et al. were able to understand, from a structural point of view, how these ligands regulate this channel, and to propose a gating mechanism that is distinct from the mechanisms that are known to control other potassium channels. DOI: http://dx.doi.org/10.7554/eLife.00184.002