Sansom M S, Balaram P, Karle I L
Laboratory of Molecular Biophysics, University of Oxford, UK.
Eur Biophys J. 1993;21(6):369-83. doi: 10.1007/BF00185864.
Zervamicin-IIB (Zrv-IIB) is a 16 residue peptaibol which forms voltage-activated, multiple conductance level channels in planar lipid bilayers. A molecular model of Zrv-IIB channels is presented. The structure of monomeric Zrv-IIB is based upon the crystal structure of Zervamicin-Leu. The helical backbone is kinked by a hydroxyproline residue at position 10. Zrv-IIB channels are modelled as helix bundles of from 4 to 8 parallel helices surrounding a central pore. The monomers are packed with their C-terminal helical segments in close contact, and the bundles are stabilized by hydrogen bonds between glutamine 11 and hydroxyproline 10 of adjacent helices. Interaction energy profiles for movement of three different probes species (K+, Cl- and water) through the central pore are analyzed. The conformations of: (a) the sidechain of glutamine 3; (b) the hydroxyl group of hydroxyproline 10; and (c) the C-terminal hydroxyl group are "optimized" in order to maximize favourable interactions between the channel and the probes, resulting in favourable interaction energy profiles for all three. This suggests that conformational flexibility of polar sidechains enables the channel lining to mimic an aqueous environment.
泽尔瓦霉素-IIB（Zrv-IIB）是一种由16个残基组成的肽菌素，它能在平面脂质双分子层中形成电压激活的多电导水平通道。本文提出了Zrv-IIB通道的分子模型。单体Zrv-IIB的结构基于泽尔瓦霉素-亮氨酸的晶体结构。螺旋主链在第10位被一个羟脯氨酸残基扭结。Zrv-IIB通道被模拟为由4至8个围绕中心孔的平行螺旋组成的螺旋束。单体的C端螺旋段紧密接触排列，相邻螺旋的谷氨酰胺11和羟脯氨酸10之间的氢键使螺旋束得以稳定。分析了三种不同探针物质（K⁺、Cl⁻和水）通过中心孔的相互作用能曲线。为了使通道与探针之间的有利相互作用最大化，对以下三种构象进行了“优化”：（a）谷氨酰胺3的侧链；（b）羟脯氨酸10的羟基；（c）C端羟基，结果这三种情况都得到了有利的相互作用能曲线。这表明极性侧链的构象灵活性使通道内衬能够模拟水环境。
