Kcsa
Kcsa
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DOI：
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发表时间：
2001
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通讯作者：
Christopher Miller
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作者：
M. LeMasurier;L. Heginbotham;Christopher Miller
在平面脂双层系统中，在单通道水平上研究了已知结构的细菌离子通道KcsA的离子传导和选择性特性。通过对称溶液电导（K+ > Rb+，NH 4+，Tl+ → Cs+，Na+，Li+）和双离子或混合离子条件下的反转电位（Tl+ > K+ > Rb+ > NH 4 + → Na+，Li+）确定了渗透离子的选择性顺序。亚毫伏精度的反转电位测定表明，K+的渗透性比Na+高150倍以上。在对称盐条件下电导随浓度的变化是复杂的，至少有两个离子结合过程揭示了自己：低于20 mM的高亲和力过程和100- 1000 mM范围内的低亲和力过程。这些特性类似于在许多真核K+通道中看到的特性，它们建立了KcsA作为真核K+通道中离子渗透的忠实结构模型。
Ion conduction and selectivity properties of KcsA, a bacterial ion channel of known structure, were studied in a planar lipid bilayer system at the single-channel level. Selectivity sequences for permeant ions were determined by symmetrical solution conductance (K+ > Rb+, NH4 +, Tl+ ≫ Cs+, Na+, Li+) and by reversal potentials under bi-ionic or mixed-ion conditions (Tl+ > K+ > Rb+ > NH4 + ≫ Na+, Li+). Determination of reversal potentials with submillivolt accuracy shows that K+ is over 150-fold more permeant than Na+. Variation of conductance with concentration under symmetrical salt conditions is complex, with at least two ion-binding processes revealing themselves: a high affinity process below 20 mM and a low affinity process over the range 100–1,000 mM. These properties are analogous to those seen in many eukaryotic K+ channels, and they establish KcsA as a faithful structural model for ion permeation in eukaryotic K+ channels.