MUTATION OF CONSERVED NEGATIVELY CHARGED RESIDUES IN THE S2 AND S3 TRANSMEMBRANE SEGMENTS OF A MAMMALIAN K+ CHANNEL SELECTIVELY MODULATES CHANNEL GATING
MUTATION OF CONSERVED NEGATIVELY CHARGED RESIDUES IN THE S2 AND S3 TRANSMEMBRANE SEGMENTS OF A MAMMALIAN K+ CHANNEL SELECTIVELY MODULATES CHANNEL GATING
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DOI：
10.1073/pnas.92.20.9422
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发表时间：
1995-09-26
影响因子：
11.1
通讯作者：
MONTAL, M
中科院分区：
文献类型：
--
作者：
PLANELLSCASES, R;FERRERMONTIEL, AV;MONTAL, M
电压门控通道蛋白感知跨膜电场的变化，并响应构象变化，使离子能够扩散穿过成孔结构。定点诱变结合两栖动物卵母细胞表达突变体的电生理分析，先前已将 S4 跨膜片段确立为电压传感器的一个元件。在这里，我们表明，大脑 K+ 通道 S2 和 S3 中保守的带负电残基的突变（被认为是 S4 中带正电残基的反向变化）选择性地调节通道门控而不改变渗透特性。S2 中中和或反向电荷的 Glu(235) 突变增加了通道开放的概率和表观门控价。相反，S3 中用 Arg 替换 Glu(272) 或用 Asp 替换 Thr(268) 会降低开放概率和表观门控价。 S2 中的残基 Glu(225) 只能被酸性残基取代，而 S3 中的 Asp(258) 不能容忍任何尝试的改变。这些结果意味着 S2 和 S3 不太可能参与通道衬里，但与 S4 一起可能是电压传感结构的附加组件。
Voltage-gated channel proteins sense a change in the transmembrane electric field and respond with a conformational change that allows ions to diffuse across the pore-forming structure, Site-specific mutagenesis combined with electrophysiological analysis of expressed mutants in amphibian oocytes has previously established the S4 transmembrane segment as an element of the voltage sensor. Here, we show that mutations of conserved negatively charged residues in S2 and S3 of a brain K+ channel, thought of as counterchanges for the positively charged residues in S4, selectively modulate channel gating without modifying the permeation properties, Mutations of Glu(235) in S2 that neutralize or reverse charge increase the probability of channel opening and the apparent gating valence. In contrast, replacements of Glu(272) by Arg or Thr(268) by Asp in S3 decrease the open probability and the apparent gating valence. Residue Glu(225) in S2 tolerated replacement only by acidic residues, whereas Asp(258) in S3 was intolerant to any attempted change, These results imply that S2 and S3 are unlikely to be involved in channel lining, yet, together with S4, may be additional components of the voltage-sensing structure.