Duclohier H, Alder G M, Bashford C L, Brückner H, Chugh J K, Wallace B A
Interactions Cellulaires et Moléculaires, UMR 6026 Centre National de la Recherche Scientifique-Université de Rennes I, 35042 Rennes Cedex, France.
Biophys J. 2004 Sep;87(3):1705-10. doi: 10.1529/biophysj.104.040659.
Trichotoxin_A50E is an 18-residue peptaibol whose crystal structure has recently been determined. In this study, the conductance properties of trichotoxin_A50E have been investigated in neutral planar lipid bilayers. The macroscopic current-voltage curves disclose a moderate voltage-sensitivity and the concentration-dependence suggests the channels are primarily hexameric. Under ion gradients, shifts of the reversal potential indicate that cations are preferentially transported. Trichotoxin displays only one single-channel conductance state in a given experiment, but an ensemble of experiments reveals a distribution of conductance levels. This contrasts with the related peptaibol alamethicin, which produces multiple channel levels in a single experiment, indicative of recruitment of additional monomers into different multimeric-sized channels. Based on these conductance measurements and on the recently available crystal structure of trichotoxin_A50E, which is a shorter and straighter helix than alamethicin, a tightly-packed hexameric model structure has been constructed for the trichotoxin channel. It has molecular dimensions and surface electrostatic potential compatible with the observed conductance properties of the most probable and longer-lived channel.
Trichotoxin_A50E是一种由18个氨基酸残基组成的肽抗生素，其晶体结构最近已被确定。在本研究中，已在中性平面脂质双分子层中研究了Trichotoxin_A50E的电导特性。宏观电流-电压曲线显示出适度的电压敏感性，浓度依赖性表明通道主要是六聚体。在离子梯度下，反转电位的变化表明阳离子优先被转运。在给定的实验中，Trichotoxin仅显示一种单通道电导状态，但一系列实验揭示了电导水平的分布。这与相关的肽抗生素短杆菌肽A形成对比，短杆菌肽A在单个实验中产生多个通道水平，表明有额外的单体被招募到不同多聚体大小的通道中。基于这些电导测量以及最近获得的Trichotoxin_A50E晶体结构（它是比短杆菌肽A更短、更直的螺旋），已构建了一个紧密堆积的Trichotoxin通道六聚体模型结构。它具有与观察到的最可能且寿命更长的通道的电导特性相兼容的分子尺寸和表面静电势。
