The mechanism underlying ion permeation through potassium channels still remains controversial. K+ ions permeate across a narrow selectivity filter (SF) in a single file. Conventional scenarios assume that K+ ions are tightly bound in the SF, and, thus, they are displaced from their energy well by ion-ion repulsion with an incoming ion. This tight coupling between entering and exiting ions has been called the "knock-on" mechanism. However, this paradigm is contradicted by experimental data measuring the water-ion flux coupling ratio, demonstrating fewer ion occupancies. Here, the results of molecular dynamics simulations of permeation through the KcsA potassium channel revealed an alternative mechanism. In the aligned ions in the SF (an ion queue), the outermost K+ was readily and spontaneously released toward the extracellular space, and the affinity of the relevant ion was ~ 50 mM. Based on this low-affinity regime, a simple queueing mechanism described by loose coupling of entering and exiting ions is proposed.

中文翻译：

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钾离子通过钾通道的到达和释放排队机制。

离子通过钾离子通道渗透的机制仍存在争议。K +离子在单个文件中穿过狭窄的选择性过滤器（SF）。传统方案假定K +离子紧紧地束缚在SF中，因此，它们会被进入离子的离子-离子排斥而从其能量井中转移出来。进入离子和离开离子之间的这种紧密耦合被称为“敲除”机制。但是，这种范例与测量水离子通量耦合比的实验数据相矛盾，表明离子占有量较少。在这里，通过KcsA钾离子通道渗透的分子动力学模拟结果揭示了另一种机制。在SF中的对齐离子（离子队列）中，最外面的K +容易并自发地释放到细胞外空间，相关离子的亲和力约为50 mM。基于这种低亲和力的机制，提出了一种简单的排队机制，该机制通过输入和输出离子的松散耦合来描述。