Department of Neuroscience and Center for Learning and Memory, The University of Texas at Austin, Austin, TX 78712.
Proc Natl Acad Sci U S A. 2014 Jan 7;111(1):E79-88. doi: 10.1073/pnas.1321697111. Epub 2013 Dec 23.
Three deep-pore locations, L312, A313, and A316, were identified in a scanning mutagenesis study of the BK (Ca(2+)-activated, large-conductance K(+)) channel S6 pore, where single aspartate substitutions led to constitutively open mutant channels (L312D, A313D, and A316D). To understand the mechanisms of the constitutive openness of these mutant channels, we individually mutated these three sites into the other 18 amino acids. We found that charged or polar side-chain substitutions at each of the sites resulted in constitutively open mutant BK channels, with high open probability at negative voltages, as well as a loss of voltage and Ca(2+) dependence. Given the fact that multiple pore residues in BK displayed side-chain hydrophilicity-dependent constitutive openness, we propose that BK channel opening involves structural rearrangement of the deep-pore region, where multiple residues undergo conformational changes that may increase the exposure of their side chains to the polar environment of the pore.
在对 BK（Ca2+激活的大电导 K+）通道 S6 孔进行扫描诱变研究时，确定了三个深孔位置 L312、A313 和 A316，其中单个天冬氨酸取代导致组成型开放的突变体通道（L312D、A313D 和 A316D）。为了了解这些突变体通道组成型开放性的机制，我们将这三个位点分别突变为其他 18 种氨基酸。我们发现，每个位点的带电或极性侧链取代导致组成型开放的突变体 BK 通道，在负电压下具有高的开放概率，以及电压和 Ca2+依赖性的丧失。鉴于 BK 通道中多个孔残基表现出侧链亲水性依赖性的组成型开放性，我们提出 BK 通道的开放涉及深孔区域的结构重排，其中多个残基发生构象变化，可能增加其侧链对孔的极性环境的暴露。
