Calcium ions open a selectivity filter gate during activation of the MthK potassium channel.
Calcium ions open a selectivity filter gate during activation of the MthK potassium channel.
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DOI：
10.1038/ncomms9342
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发表时间：
2015-09-23
影响因子：
16.6
通讯作者：
Nimigean CM
中科院分区：
文献类型：
--
作者：
Posson DJ;Rusinova R;Andersen OS;Nimigean CM
离子通道的打开和关闭是细胞信号传导和体内平衡的基础。控制K+通道活性的门被发现在细胞内孔收缩和细胞外侧附近的选择性过滤器内，但打开Ca2+激活的K+通道的门的具体位置仍然难以捉摸。使用甲烷杆菌thermoautotrophicum同系物（MthK）和停流荧光测定快通道激活，我们表明，细胞内季铵阻滞剂结合到封闭的MthK通道。由于已知阻断剂结合在中央通道腔内，经过细胞内入口通道，因此门必须在选择性过滤器内。此外，阻滞剂进入封闭通道的速度比开放通道慢，表明细胞内入口通道在孔关闭后变窄，而不阻止阻滞剂或较小的K+进入。因此，MthK中的Ca2+依赖性门控发生在选择性过滤器处，细胞内螺旋的耦合运动。 离子通道打开和关闭以允许离子通过膜的调节通道。在这里，作者使用选择性离子通道阻断剂来分析钾通道中的这种调节，并表明门在选择性过滤器中，经过通道的入口。
Ion channel opening and closing are fundamental to cellular signalling and homeostasis. Gates that control K+ channel activity were found both at an intracellular pore constriction and within the selectivity filter near the extracellular side but the specific location of the gate that opens Ca2+-activated K+ channels has remained elusive. Using the Methanobacterium thermoautotrophicum homologue (MthK) and a stopped-flow fluorometric assay for fast channel activation, we show that intracellular quaternary ammonium blockers bind to closed MthK channels. Since the blockers are known to bind inside a central channel cavity, past the intracellular entryway, the gate must be within the selectivity filter. Furthermore, the blockers access the closed channel slower than the open channel, suggesting that the intracellular entryway narrows upon pore closure, without preventing access of either the blockers or the smaller K+. Thus, Ca2+-dependent gating in MthK occurs at the selectivity filter with coupled movement of the intracellular helices. Ion channels open and close to allow the regulated passage of ions through the membrane. Here the authors use selective ion channel blockers to analyse this regulation in a potassium channel and show that the gate is in the selectivity filter, past the entrance to the channel.