Permeation properties of inward-rectifier potassium channels and their molecular determinants.
Permeation properties of inward-rectifier potassium channels and their molecular determinants.
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DOI：
10.1085/jgp.115.4.391
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发表时间：
2000-04
影响因子：
3.8
通讯作者：
Palmer, LG
中科院分区：
文献类型：
--
作者：
Choe, H;Sackin, H;Palmer, LG
在非洲爪蟾卵母细胞中异源表达的内向整流K+通道ROMK 2（Kir1.1b），IRK 1（Kir2.1）及其嵌合体中，研究了K通道中离子渗透和选择性的结构域。膜片钳记录的单通道中获得的细胞附着模式与不同的渗透阳离子在移液管。对于内向K+传导，用IRK 1的细胞外环替换ROMK 2的细胞外环使单通道电导增加25 pS（从39 pS增加到63 pS），而用IRK 1的COOH末端替换ROMK 2的COOH末端使电导减少16 pS（从39 pS减少到22 pS）。这些影响是加性的，独立的起源的NH 2末端或跨膜结构域，这表明这两个域形成两个电阻器串联。IRK 1的细胞外环的较大电导归因于在GYG基序前面的3个残基的3 P位置处的单个氨基酸差异（Thr与瓦尔）。两个通道对传导离子的渗透性顺序相似：Tl+ > K+ > Rb+ > NH 4+。ROMK 2的离子选择性顺序为NH 4+（1.6）> K+（1）> Tl+（0.5）> Rb+（0.4）。IRK 1的顺序为K+（1）> Tl+（0.8）> NH 4+（0.6）>> Rb+（0.1）。NH 4 +/ K+电导率（1.6）和渗透率（0.09）的比例的差异可以解释，如果NH 4+结合的亲和力低于K+的孔隙内的网站。NH 4+和Rb+通过IRK 1的相对低的电导再次归因于P区域内的3 P位置。定点突变表明，IRK 1的选择性模式需要在这个位置上的Thr或Ser。相反，COOH-末端结构域赋予IRK 1中相对高的T1+电导。我们建议，P-区域和COOH末端有助于独立的孔的电导和选择性性能。
The structural domains contributing to ion permeation and selectivity in K channels were examined in inward-rectifier K+ channels ROMK2 (Kir1.1b), IRK1 (Kir2.1), and their chimeras using heterologous expression in Xenopus oocytes. Patch-clamp recordings of single channels were obtained in the cell-attached mode with different permeant cations in the pipette. For inward K+ conduction, replacing the extracellular loop of ROMK2 with that of IRK1 increased single-channel conductance by 25 pS (from 39 to 63 pS), whereas replacing the COOH terminus of ROMK2 with that of IRK1 decreased conductance by 16 pS (from 39 to 22 pS). These effects were additive and independent of the origin of the NH2 terminus or transmembrane domains, suggesting that the two domains form two resistors in series. The larger conductance of the extracellular loop of IRK1 was attributable to a single amino acid difference (Thr versus Val) at the 3P position, three residues in front of the GYG motif. Permeability sequences for the conducted ions were similar for the two channels: Tl+ > K+ > Rb+ > NH4 +. The ion selectivity sequence for ROMK2 based on conductance ratios was NH4 + (1.6) > K+ (1) > Tl+ (0.5) > Rb+ (0.4). For IRK1, the sequence was K+ (1) > Tl+ (0.8) > NH4 + (0.6) >> Rb+ (0.1). The difference in the NH4 +/ K+ conductance (1.6) and permeability (0.09) ratios can be explained if NH4 + binds with lower affinity than K+ to sites within the pore. The relatively low conductances of NH4 + and Rb+ through IRK1 were again attributable to the 3P position within the P region. Site-directed mutagenesis showed that the IRK1 selectivity pattern required either Thr or Ser at this position. In contrast, the COOH-terminal domain conferred the relatively high Tl+ conductance in IRK1. We propose that the P-region and the COOH terminus contribute independently to the conductance and selectivity properties of the pore.
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影响因子：
56.9
作者：
Doyle, DA;Cabral, JM;MacKinnon, R
通讯作者：
MacKinnon, R
影响因子：
3.4
作者：
HEGINBOTHAM, L;MACKINNON, R
通讯作者：
MACKINNON, R
DOI：
10.1085/jgp.58.4.413
发表时间：
1971-10
期刊：
The Journal of general physiology
影响因子：
--
作者：
Armstrong CM
通讯作者：
Armstrong CM
影响因子：
5.5
作者：
BEGENISICH, TB;CAHALAN, MD
通讯作者：
CAHALAN, MD
影响因子：
5.5
作者：
HORIE, M;IRISAWA, H;NOMA, A
通讯作者：
NOMA, A