Laboratory of Molecular Biophysics, Department of Physics, Universitat Jaume I, 12071 Castellón, Spain.
Section on Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Int J Mol Sci. 2019 Feb 5;20(3):674. doi: 10.3390/ijms20030674.
The outer membrane of Gram-negative bacteria contains β-barrel proteins that form high-conducting ion channels providing a path for hydrophilic molecules, including antibiotics. Traditionally, these proteins have been considered to exist only in an open state so that regulation of outer membrane permeability was accomplished via protein expression. However, electrophysiological recordings show that β-barrel channels respond to transmembrane voltages by characteristically switching from a high-conducting, open state, to a so-called 'closed' state, with reduced permeability and possibly exclusion of large metabolites. Here, we use the bacterial porin OmpF from as a model system to gain insight on the control of outer membrane permeability by bacterial porins through the modulation of their open state. Using planar bilayer electrophysiology, we perform an extensive study of the role of membrane lipids in the OmpF channel closure by voltage. We pay attention not only to the effects of charges in the hydrophilic lipid heads but also to the contribution of the hydrophobic tails in the lipid-protein interactions. Our results show that gating kinetics is governed by lipid characteristics so that each stage of a sequential closure is different from the previous one, probably because of intra- or intermonomeric rearrangements.
革兰氏阴性细菌的外膜含有β-桶状蛋白，这些蛋白形成高导电性的离子通道，为亲水分子（包括抗生素）提供了通道。传统上，这些蛋白质被认为只存在于开放状态，因此通过蛋白质表达来调节外膜通透性。然而，电生理记录显示，β-桶状通道会对跨膜电压做出反应，特征是从高导电性的开放状态切换到所谓的“关闭”状态，通透性降低，可能会排斥大的代谢物。在这里，我们使用来自 的细菌孔蛋白 OmpF 作为模型系统，通过调节其开放状态，深入了解细菌孔蛋白对外膜通透性的控制。我们使用平面双层电生理学，对电压调节 OmpF 通道关闭过程中膜脂的作用进行了广泛的研究。我们不仅关注亲水头的电荷效应，还关注疏水尾在脂-蛋白相互作用中的贡献。我们的结果表明，门控动力学受脂质特性的控制，因此连续关闭的每个阶段都与前一个阶段不同，这可能是由于单体内部或单体间的重排。
