Interaction of internal Ba2+ with a cloned Ca(2+)-dependent K+ (hslo) channel from smooth muscle.
Interaction of internal Ba2+ with a cloned Ca(2+)-dependent K+ (hslo) channel from smooth muscle.
复制标题
内部BA2+与平滑肌的克隆Ca（2+） - 依赖性K+（HSLO）通道的相互作用。
DOI：
10.1085/jgp.107.3.399
复制
发表时间：
1996-03
影响因子：
3.8
通讯作者：
Latorre, R
中科院分区：
文献类型：
--
作者：
Diaz, F;Wallner, M;Stefani, E;Toro, L;Latorre, R
我们研究了通过克隆的人子宫肌层 Ca(2+) 依赖性 K+ 通道 (hslo) 的钾电流。电流被记录在非洲爪蟾卵母细胞膜的由内而外的大斑块中。特别是，评估了这些通道在高正电位下表现出的类似失活过程，以探索其分子性质。这种电流抑制使电流-电压曲线呈钟形。该过程的动力学和电压依赖性表明 Ba2+ 块的可能性。在零添加 Ba2+ 和 hslo 通道内部 Ba2+ 阻断处观察到的失活过程有以下相似之处： (a) 在稳态下，在零添加 Ba2+ 处观察到的电流抑制的电压依赖性与 Ba2+ 阻断的电压依赖性相同； (b) 零添加 Ba2+ 时电流衰减恢复的时间常数与 Ba2+ 阻断电流恢复的时间常数相同； (c) 通过向内部溶液中添加 Ba2+ 螯合剂 [(+)-18-冠-6-四羧酸]，两种情况下的电流衰减都得到了很大程度的抑制。在我们的实验条件下，我们确定复合螯合剂 Ba2+ 的 Kd 为 1.6 x 10(-10) M。我们得出的结论是，在内部溶液中零添加 Ba2+ 时观察到的电流衰减是由于溶液中存在污染物 Ba2+（大约 70 nM），而不是固有的门控过程。 hslo 通道中的 Ba2+ 阻断反应是双分子的。 Ba2+ 结合到一个位点（零外加电压下 Kd = 0.36 +/- 0.05 mM），该位点可感应内膜表面 92 +/- 25% 的电位降。
We have studied potassium currents through a cloned Ca(2+)-dependent K+ channel (hslo) from human myometrium. Currents were recorded in inside- out macropatches from membranes of Xenopus laevis oocytes. In particular, the inactivation-like process that these channels show at high positive potentials was assessed in order to explore its molecular nature. This current inhibition conferred a bell shape to the current- voltage curves. The kinetic and voltage dependence of this process suggested the possibility of a Ba2+ block. There were the following similarities between the inactivation process observed at zero-added Ba2+ and the internal Ba2+ block of hslo channels: (a) in the steady state, the voltage dependence of the current inhibition observed at zero-added Ba2+ was the same as the voltage dependence of the Ba2+ block; (b) the time constant for recovery from current decay at zero- added Ba2+ was the same as the time constant for current recovery from Ba2+ blockade; and (c) current decay was largely suppressed in both cases by adding a Ba2+ chelator [(+)-18-crown-6-tetracarboxylic acid] to the internal solution. In our experimental conditions, we determined that the Kd for the complex chelator-Ba2+ is 1.6 x 10(-10) M. We conclude that the current decay observed at zero-added Ba2+ to the internal solution is due to contaminant Ba2+ present in our solutions (approximately 70 nM) and not to an intrinsic gating process. The Ba2+ blocking reaction in hslo channels is bimolecular. Ba2+ binds to a site (Kd = 0.36 +/- 0.05 mM at zero applied voltage) that senses 92 +/- 25% of the potential drop from the internal membrane surface.