Some algal viruses have coding sequences for proteins with structural and functional characteristics of pore modules of complex K⁺ channels. Here we exploit the structural diversity among these channel orthologs to discover new basic principles of structure/function correlates in K⁺ channels. The analysis of three similar K⁺ channels with ≤ 86 amino acids (AA) shows that one channel (Kmpv₁) generates an ohmic conductance in HEK293 cells while the other two (Kmpv_SP1, Kmpv_PL1) exhibit typical features of canonical Kir channels. Like Kir channels, the rectification of the viral channels is a function of the K⁺ driving force. Reconstitution of Kmpv_SP1 and Kmpv_PL1 in planar lipid bilayers showed rapid channel fluctuations only at voltages negative of the K⁺ reversal voltage. This rectification was maintained in KCl buffer with 1 mM EDTA, which excludes blocking cations as the source of rectification. This means that rectification of the viral channels must be an inherent property of the channel. The structural basis for rectification was investigated by a chimera between rectifying and non-rectifying channels as well as point mutations making the rectifier similar to the ohmic conducting channel. The results of these experiments exclude the pore with pore helix and selectivity filter as playing a role in rectification. The insensitivity of the rectifier to point mutations suggests that tertiary or quaternary structural interactions between the transmembrane domains are responsible for this type of gating.

一些藻类病毒具有蛋白质的编码序列，该蛋白质具有复杂K ⁺通道的孔模块的结构和功能特征。在这里，我们利用这些通道直系同源物之间的结构多样性来发现K ⁺通道中结构/功能相关的新基本原理。对三个具有≤86个氨基酸（AA）的相似K ⁺通道的分析表明，一个通道（Kmpv ₁）在HEK293细胞中产生了欧姆电导，而其他两个通道（Kmpv _SP1，Kmpv _PL1）则显示了典型Kir通道的典型特征。像Kir通道一样，病毒通道的整流是K ⁺驱动力的函数。重组Kmpv平面脂质双层中的_SP1和Kmpv _PL1仅在K ⁺负电压下显示快速通道波动反转电压。该精馏保持在具有1mM EDTA的KCl缓冲液中，其排除了封闭阳离子作为精馏源。这意味着病毒通道的整流必须是通道的固有属性。整流的结构基础是通过整流和非整流通道之间的嵌合体以及使整流器类似于欧姆导电通道的点突变来研究的。这些实验的结果排除了具有孔螺旋的孔和选择性过滤器在精馏中的作用。整流器对点突变的不敏感性表明跨膜结构域之间的三级或四级结构相互作用是这种类型的门控的原因。