Gordon L G, Haydon D A
Philos Trans R Soc Lond B Biol Sci. 1975 Jun 10;270(908):433-47. doi: 10.1098/rstb.1975.0021.
This article is concerned primarily with the mechanism of the potential-dependent conductance induced in artificial lipid membranes by the cyclic polypeptide andibiotic alamethicin. It has already been shown from studies of the fluctuations that can be detected in very small membrane currents that alamethicin forms transient pores of some 0.6 nm in diameter and that, for small inorganic ions, these are poorly selective. The origin of these pores, their spatial distribution and interaction are discussed. It is demonstrated that the sensitivity of the membrane conductance to the applied potential arises only to a slight extent from the current-voltage relations for the individual pores, and that the main effect stems from the influence of the potential on the frequency of opening of the pores. From the properties of lipid membranes containing alamethicin in a wide variety of electrolytes, and from other evidence, it is concluded that the polypeptide reacts to the electric field more probably because it has dipole moment than because it binds ions. It is proposed that the conducting complex is capable of functioning in either of two orientations, and that it is these two possibilities that give rise to certain differences in the single channel characteristics for the two directions of the field.
本文主要关注环状多肽短杆菌肽A在人工脂质膜中诱导产生的电位依赖性电导的机制。通过对非常小的膜电流中可检测到的波动进行研究已经表明，短杆菌肽A形成了直径约为0.6纳米的瞬时孔，并且对于小的无机离子而言，这些孔的选择性很差。本文讨论了这些孔的起源、空间分布及其相互作用。结果表明，膜电导对施加电位的敏感性仅在一定程度上源于单个孔的电流 - 电压关系，而主要效应源于电位对孔开放频率的影响。根据在多种电解质中含有短杆菌肽A的脂质膜的性质以及其他证据，得出的结论是，多肽对电场作出反应更可能是因为它具有偶极矩，而不是因为它结合离子。有人提出，导电复合物能够以两种取向中的任何一种发挥作用，正是这两种可能性导致了电场两个方向的单通道特性存在某些差异。
