Calcium-dependent potassium channel in Paramecium studied under patch clamp.
Calcium-dependent potassium channel in Paramecium studied under patch clamp.
复制标题
在膜片钳下研究草履虫中的钙依赖性钾通道。
DOI：
10.1007/bf01871166
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Martinac,B
中科院分区：
文献类型：
--
作者：
Saimi,Y;Martinac,B
We have studied a class of Cai2+-dependent K channels in inside-out excised membrane patches fromParameciumunder patch clamp. Single channels had a conductance of 72 ±9.0 pS in a solution containing 100mMK+. The channels were selective for K+over Rb+with the permeability ratio of 1∶ 0.56. and over Na+, Cs+or NH4+with a ratio 1∶<0.1. The channel activity was dependent on Cai2+, which was applied to the cytoplasmic side; the Cai2+concentration for the half maximal activation was 2 μm. The Hill coefficient for the Cai2+dependence of the channel activity was 2.58, indicating that more than two Cai2+bindings are necessary for full activation. Unlike most Cai2+-dependent K channels in other organisms, the channels inParameciumwere slightly more active upon hyperpolarization than upon depolarization. The voltage dependence was fitted to a Boltzmann curve with 41.2 mV pere-fold change in channel activity. While a high Cai2+concentration activated the channels, it also irreversibly reduced the channel activity over time. The decay of channel activity occurred faster at higher Cai2+concentrations. Quaternary ammonium ions suppressed ion passage through the channel; more highly alkylated quaternary ammonium ions were more efficient in blocking. Bai2+and Cai2+were relatively ineffective in blockage. It was concluded that these Cai2+-dependent K channels inParameciumare different from the previously described Cai2+-dependent K channels, and are perhaps of a novel class.
