Berry R M, Edmonds D T
Clarendon Laboratory, Oxford, UK.
J Membr Biol. 1993 Apr;133(1):77-84. doi: 10.1007/BF00231879.
Many ion channels that normally gate fully open or shut have recently been observed occasionally to display well-defined subconductance states with conductances much less than those of the fully open channel. One model of this behavior is a channel consisting of several parallel pores with a strong correlation between the flux in each pore such that, normally, they all conduct together but, under special circumstances, the pores may transfer to a state in which only some of them conduct. This paper introduces a general technique for modeling correlated pores, and explores in detail by computer simulation a particular model based upon electric interaction between the pores. Correlation is obtained when the transient electric field of ions passing through the pores acts upon a common set of ionizable residues of the channel protein, causing transient changes in their effective pK and hence in their charged state. The computed properties of such a correlated parallel pore channel with single occupation of each pore are derived and compared to those predicted for a single pore that can contain more than one ion at a time and also to those predicted for a model pore with fluctuating barriers. Experiments that could distinguish between the present and previous models are listed.
最近观察到，许多通常完全打开或关闭的离子通道偶尔会呈现出明确的亚电导状态，其电导远低于完全打开通道的电导。对此行为的一种模型是，通道由几个平行的孔组成，每个孔中的通量之间存在强相关性，使得通常情况下它们都一起传导，但在特殊情况下，这些孔可能会转变为只有部分孔传导的状态。本文介绍了一种对相关孔进行建模的通用技术，并通过计算机模拟详细探讨了基于孔之间电相互作用的特定模型。当离子穿过孔时的瞬态电场作用于通道蛋白的一组共同的可电离残基，导致其有效pK发生瞬态变化，进而导致其带电状态发生变化时，就会产生相关性。推导了每个孔仅容纳一个离子的这种相关平行孔通道的计算特性，并将其与一次可容纳多个离子的单个孔所预测的特性以及具有波动势垒的模型孔所预测的特性进行了比较。列出了可以区分当前模型和先前模型的实验。
