External barium block of Shaker potassium channels: evidence for two binding sites.
External barium block of Shaker potassium channels: evidence for two binding sites.
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DOI：
10.1085/jgp.106.6.1069
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发表时间：
1995-12
期刊：
影响因子：
--
通讯作者：
Stefani E
中科院分区：
文献类型：
--
作者：
Hurst RS;Latorre R;Toro L;Stefani E
外部钡离子抑制表达ShH4 δ 6-46的爪蟾卵母细胞的K+电流，这是Shaker K+通道的非失活缺失。在宏观层面上，Ba2+块由快、慢两部分组成。与慢速组分相比，快速组分对Ba2+的敏感性较低（在0 mV时的表观解离常数K(0)，约为19.1 mM），并且对电压的依赖性也较小（视电距离，δ，约为0.14）。慢速组分（K(0)，约9.4 mM， δ约0.25）被向外的K+电流缓解，这表明相应的结合位点位于通道传导途径内。在单通道水平上，阻滞的快速成分表现为幅度的明显降低，表明阻滞和解封反应非常迅速。相反，慢组件似乎与从去极化命令开始出现的长阻塞时间有关。慢速组件的安装比扩散限制过程慢得多；例如，2 mM Ba2+产生的阻断时间常数（tau）约为159秒（保持电位，HP = -90 mV）。然而，这种慢速组分的阻断率不是外部Ba2+的线性函数，并且在高浓度时趋于饱和。这与简单的双分子阻断反应不一致。外部Ba2+阻滞的这些特征可以用两个连续Ba2+结合位点的简单模型来解释，其中两个位点的较深产生阻滞的慢组分。
External barium ions inhibit K+ currents of Xenopus oocytes expressing ShH4 delta 6-46, the non-inactivating deletion of the Shaker K+ channel. At the macroscopic level, Ba2+ block comprises both a fast and a slow component. The fast component is less sensitive to Ba2+ (apparent dissociation constant at 0 mV, K(0), approximately 19.1 mM) than the slow component and is also less voltage dependent (apparent electrical distance, delta, approximately 0.14). The slow component (K(0), approximately 9.4 mM, delta approximately 0.25) is relieved by outward K+ current, which suggests that the corresponding binding site resides within the channel conduction pathway. At the single channel level, the fast component of block is evidenced as an apparent reduction in amplitude, suggesting an extremely rapid blocking and unblocking reaction. In contrast, the slow component appears to be associated with long blocked times that are present from the beginning of a depolarizing command. Installation of the slow component is much slower than a diffusion limited process; for example, the blocking time constant (tau) produced by 2 mM Ba2+ is approximately 159 s (holding potential, HP = -90 mV). However, the blocking rate of this slow component is not a linear function of external Ba2+ and tends to saturate at higher concentrations. This is inconsistent with a simple bi-molecular blocking reaction. These features of external Ba2+ block can be accounted for by a simple model of two sequential Ba2+ binding sites, where the deeper of the two sites produces the slow component of block.
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影响因子：
2.9
作者：
MACKINNON, R;LATORRE, R;MILLER, C
通讯作者：
MILLER, C
影响因子：
64.8
作者：
LOPEZ, GA;JAN, YN;JAN, LY
通讯作者：
JAN, LY
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：
64.8
作者：
IMOTO, K;METHFESSEL, C;NUMA, S
通讯作者：
NUMA, S
影响因子：
16.2
作者：
NEWLAND, CF;ADELMAN, JP;ALMERS, W
通讯作者：
ALMERS, W