VOLTAGE-DEPENDENT SLOWING OF K-CHANNEL CLOSING KINETICS BY RB+
VOLTAGE-DEPENDENT SLOWING OF K-CHANNEL CLOSING KINETICS BY RB+
复制标题
DOI：
10.1085/jgp.98.3.535
复制
发表时间：
1991-09-01
影响因子：
3.8
通讯作者：
MATTESON, DR
中科院分区：
文献类型：
--
作者：
SALA, S;MATTESON, DR
我们研究了Rb ~+对蟾鱼胰岛细胞钾通道关闭动力学的影响。这些通道是电压依赖性的，在-10 mV的正电压下激活。通道也在延长的去极化后失活，失活时间过程最适合两个指数的总和。瞬时电流-电压关系表明，外部Rb+进入通道容易K+，但携带较少的电流。在-140到-50 mV的电压范围内，通道的关闭时间过程可以用单个指数拟合。当Rb+存在于外部溶液中时，通道关闭得更慢。这种Rb+效应的大小是电压依赖性的，在更负的电压下减小。同样，当内溶液中含有Rb+而不是K+时，关闭时间常数增加。内部Rb+的影响也是电压依赖性的;在电压为正到-80 mV时，内部Rb+的闭合时间常数比K+慢，而在更负的电压下，差异可以忽略不计。与内部Rb+，关闭时间常数和电压之间的关系是最好的拟合与两个指数分量，表明存在两个不同的电压依赖性过程。结果进行了讨论，在一个模型的K通道与两个内部结合位点，我们得出结论，Rb+产生的通道门控结合到一个网站在孔的影响。
We have studied the effect of Rb+ on K channel closing kinetics in toadfish pancreatic islet cells. These channels are voltage dependent, activating at voltages positive to -10 mV. The channels also inactivate upon prolonged depolarizations, and the inactivation time course is best fit by the sum of two exponentials. Instantaneous current-voltage relationships show that external Rb+ enters the channel as easily as K+, but carries less current. In the voltage range from -140 to -50 mV, the closing time course of the channels can be fit with a single exponential. When Rb+ is present in the external solution the channels close more slowly. The magnitude of this Rb+ effect is voltage dependent, decreasing at more negative voltages. Similarly, when the internal solution contains Rb+ instead of K+ the closing time constants are increased. The effect of internal Rb+ is also voltage dependent; at voltages positive to -80 mV the closing time constant in internal Rb+ is slower than in K+, whereas at more negative voltages the difference is negligible. With internal Rb+, the relationship between the closing time constant and voltage is best fit with two exponential components, suggesting the presence of two distinct voltage-dependent processes. The results are discussed in terms of a model of the K channel with two internal binding sites, and we conclude that Rb+ produces its effects on channel gating by binding to a site in the pore.