Membrane dipole potential modulates proton conductance through gramicidin channel: movement of negative ionic defects inside the channel.
Membrane dipole potential modulates proton conductance through gramicidin channel: movement of negative ionic defects inside the channel.
复制标题
膜偶极电位通过短杆菌肽通道调节质子电导：通道内负离子缺陷的运动。
DOI：
10.1016/s0006-3495(02)75448-9
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发表时间：
2002
影响因子：
3.4
通讯作者：
Antonenko,YuriN
中科院分区：
文献类型：
--
作者：
Rokitskaya,TatyanaI;Kotova,ElenaA;Antonenko,YuriN
研究了膜偶极电位对双层脂膜 (BLM) 中短杆菌肽通道活性的影响。值得注意的是，与 gA 碱金属阳离子电导相比，短杆菌肽 A (gA) 通道的质子电导对偶极电位的调节反应相反。特别是，添加已知可降低膜偶极电位的根皮素，一方面导致 gA 质子电导降低，另一方面导致 gA 碱金属电导增加，而 6-酮胆甾醇（提高膜偶极电位的试剂）引起 gA 质子电导增加，而不是碱金属阳离子电导减少。 6-酮胆甾醇效应的特殊性在于其对 H+ 浓度的依赖性。使用不渗透偶极化合物根皮苷的实验表明，如果仅改变 BLM 的一个单层或两个单层的偶极电位，则通过短杆菌肽通道的质子传输对改变膜偶极电位的响应不会发生质的变化。与 gA 质子电导相反，单通道寿命随着膜偶极电位的变化而变化，无论渗透阳离子（质子或钾离子）的种类如何。这项研究的结果可以通过以下假设来初步解释：通过短杆菌肽通道的质子传导的限速步骤之一实际上代表带负电的物质（负离子缺陷）穿过膜的运动。
The effect of membrane dipole potential on gramicidin channel activity in bilayer lipid membranes (BLMs) was studied. Remarkably, it appeared that proton conductance of gramicidin A (gA) channels responded to modulation of the dipole potential oppositely as compared with gA alkali metal cation conductance. In particular, the addition of phloretin, known to reduce the membrane dipole potential, resulted in a decrease in gA proton conductance, on one hand, and an increase in gA alkali metal conductance, on the other hand, whereas 6-ketocholestanol, the agent raising the membrane dipole potential, provoked an increase in gA proton conductance as opposed to a decrease in the alkali metal cation conductance. The peculiarity of the 6-ketocholestanol effect consisted in its dependence on the H+concentration. The experiments with the impermeant dipolar compound, phloridzin, showed that the response of proton transport through gramicidin channels to varying the membrane dipole potential did not change qualitatively if the dipole potential of only one monolayer or both monolayers of the BLM was altered. In contrast to gA proton conductance, the single-channel lifetime changed similarly with varying the membrane dipole potential, regardless of the kind of permeant cations (protons or potassium ions). The results of this study could be tentatively accounted for by an assumption that one of the rate-limiting steps of proton conduction through gramicidin channels represents, in fact, movement of negatively charged species (negative ionic defects) across a membrane.