Anemone toxin II unmasks two conductance states in neuronal sodium channels.
Anemone toxin II unmasks two conductance states in neuronal sodium channels.
复制标题
海葵毒素 II 揭示神经元钠通道中的两种电导状态。
DOI：
10.1016/0006-8993(96)00566-5
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发表时间：
1996
期刊：
影响因子：
2.9
通讯作者：
Recio-Pinto,E
中科院分区：
文献类型：
--
作者：
Castillo,C;Piernavieja,C;Recio-Pinto,E
研究了海葵毒素II(ATX)修饰的平面脂质双层膜上的电压依赖性神经元钠通道。ATx修饰的通道呈现两种主要的导电状态：短暂(ms-S)高电导(≈65ps)状态和长寿命(S-分钟)低电导(≈10ps)状态。高电导状态经历了短暂闭合(Ms)，低电导状态经历了长时间闭合(S)。检测到这些状态的概率与时间和电压有关。由于高电导状态，通道的分数开放时间(Fo)随去极化而增加，中点电位(Va)为−36 mV，表观门控电荷(Za)为2.8。由于低电导态引起的沟道FOF随去极化而增大，其Vaof为+13 mV，Zaa值为1.4。在正电位下，ATX修饰的通道缓慢地(分钟)进入吸收非导电状态。在低电导和高电导状态下，Na+/K+的渗透率比分别为2和4。岩藻毒素类似物C3以高亲和力阻断ATX修饰的钠通道(Kd(60-90 mV)=410 nM，0.5MNaC l)。数据表明，在去极化步骤后，ATX修饰的通道迅速(Ms)进入高电导状态，而更慢(S-分钟)进入低电导状态。此外，随着膜电位变得更正，平衡从高电导状态转移到低电导状态，从导电态转移到吸收非导电态。
Anemone toxin II (ATX)-modified voltage-dependent neuronal sodium channels were studied in planar lipid bilayers. ATX-modified channels displayed two predominant conducting states: a short-lived (ms-s) high-conductance (≈ 65 pS) state and a long-lived (s-min) low-conductance (≈ 10 pS) state. The high-conductance state underwent brief closures (ms) and the low-conductance state underwent long closures (s). The probability of detecting these states was time- and voltage-dependent. The channel's fractional open time (fo) due to the high-conductance state increased with depolarization and had a midpoint potential (Va) of − 36 mV and an apparent gating charge (za) of 2.8. The channel's fodue to the low-conductance state increased with depolarization and had a Vaof + 13 mV and a zaof 1.4. At positive potentials, ATX-modified channels slowly (minutes) entered an absorbing non-conducting state. The permeability ratio of Na+/K+was 2 and 4 for the low- and high-conductance states, respectively. The saxitoxin analog C3 blocked ATX-modified sodium channels with high affinity (Kd(60–90 mV) = 410 nM, 0.5 M NaCl). The data suggest that upon a depolarization step, ATX-modified channels enter rapidly (ms) into a high-conductance state and more slowly (s-min) into a low-conductance state. Also as the membrane potential becomes more positive, the equilibrium is shifted from the high- to the low-conductance state and from the conducting states to an absorbing non-conducting state.