Gramicidin forms multi-state rectifying channels
Gramicidin forms multi-state rectifying channels
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DOI：
10.1038/294371a0
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发表时间：
1981-11-01
期刊：
影响因子：
64.8
通讯作者：
Szabo, Gabor
中科院分区：
文献类型：
--
作者：
Busath, David;Szabo, Gabor
短杆菌肽A是L和D氨基酸交替的十五肽。在细胞膜中，它形成分子尺度的阳离子传导通道（2）（3，4），在许多方面类似于（2-7）可兴奋细胞的通道（8，9）。由于这个原因，也因为它的结构已经很好地确定（1，10，11），短杆菌肽通道被认为是细胞膜中离子通道的有用模型。虽然短杆菌肽通道的性质已经被广泛研究（12），但它通常被描述为具有与在13通道的寿命期间保持不变的明确定义的电导相关的单一状态。我们在此报告，事实上，短杆菌肽A可以假设其他，导电性较低的“微型”（mini）我们观察到单个开放通道电导的自发转变和观察到大量的弱传导通道。不同沟道状态的电流-电压（I-V）关系显著不同，并且对于最小值，通常是不对称的。我们的研究结果表明，短杆菌肽通道有各种各样的稳定的构象状态，从而产生不同的电性能的通道。由于状态之间的转换发生相对不频繁，这些构象状态必须由相对较大的相互转换能量分开。类似的转换，由电场或激动剂分子保持平衡，可能是细胞膜门控通道功能的基础。
Gramicidin A is a pentadecapeptide of alternating L and D amino acids. In membranes it forms cation conductive channels(2) of molecular dimensions(3,4) that in many respects resemble(2-7) the channels of excitable cells(8,9). For this reason, and also because its structure is well established(1,10,11), the gramicidin channel is regarded as a useful model of ion channels in cell membranes. Although the properties of the gramicidin channel have been studied extensively(12), it has generally been described as having a single state associated with a sharply defined conductance that remains unaltered during the lifetime of the 13 channel We report here that, in fact, gramicidin A can assume other, less conductive 'miniature' (mini) states evidenced by our observations of spontaneous transitions in the conductance of single open channels and the observation of a significant number of weakly conducting channels. Current-voltage (I-V) relationships for different channel states differ significantly and, for minis, are often asymmetrical. Our results indicate that the gramicidin channel has a wide variety of stable conformational states that give rise to channels with different electrical properties. Because transitions between states occur relatively infrequently, these conformational states must be separated by relatively large energies of interconversion. Similar transitions, poised by the electric field or an agonist molecule, may underlie the function of gated channels in cell membranes.