Draber S, Hansen U P
Institut für Angewandte Physik der Universität Kiel, Germany.
Biophys J. 1994 Jul;67(1):120-9. doi: 10.1016/S0006-3495(94)80461-8.
The Cs+ block of K+ channels has often been investigated by methods that allow only indirect estimation of the rate constants of blocking and re-opening. This paper presents single-channel records with high temporal resolution which make the direct observation of the fast transitions between the blocked and the unblocked state possible. The rate constants kOGb, kGbO of Cs(+)-dependent blocking and of re-opening are evaluated from the time constants found in the open-time and closed-time histograms. The blocking rate constant kOGb between 1000 and 50000 s-1 depends linearly on the Cs+ concentration and strongly on voltage, increasing by a factor of 1.44 per 10 mV hyperpolarization. The re-opening rate constant kGbO approximately 30000 s-1 is independent of Cs+ concentration and only slightly voltage-dependent. Formally, the results can be described by a Woodhull-model. The strong voltage dependence with d > 1, however, weakens its plausibility. The results are interpreted in terms of a molecular framework emerging from recent results on the structure of voltage-gated channels.
钾通道的Cs⁺阻断作用常常通过仅能间接估算阻断和重新开放速率常数的方法来研究。本文展示了具有高时间分辨率的单通道记录，使得直接观察阻断态和非阻断态之间的快速转变成为可能。Cs⁺依赖性阻断和重新开放的速率常数kOGb、kGbO是根据开放时间和关闭时间直方图中的时间常数来评估的。在1000至50000 s⁻¹之间的阻断速率常数kOGb线性依赖于Cs⁺浓度，且强烈依赖于电压，每超极化10 mV增加1.44倍。重新开放速率常数kGbO约为30000 s⁻¹，与Cs⁺浓度无关，仅略微依赖于电压。形式上，结果可用伍德胡尔模型来描述。然而，d > 1时的强电压依赖性削弱了其合理性。这些结果是根据从电压门控通道结构的最新研究成果中得出的分子框架来解释的。
