Institute for Cell and Molecular Biosciences, The Medical School, Newcastle University, Newcastle Upon Tyne NE2 4HH, UK.
Department of Physics, University of Cagliari, Monserrato, Cagliari, Italy.
Structure. 2018 May 1;26(5):708-721.e4. doi: 10.1016/j.str.2018.03.010. Epub 2018 Apr 12.
The outer membranes (OM) of many Gram-negative bacteria contain general porins, which form nonspecific, large-diameter channels for the diffusional uptake of small molecules required for cell growth and function. While the porins of Enterobacteriaceae (e.g., E. coli OmpF and OmpC) have been extensively characterized structurally and biochemically, much less is known about their counterparts in Vibrionaceae. Vibrio cholerae, the causative agent of cholera, has two major porins, OmpU and OmpT, for which no structural information is available despite their importance for the bacterium. Here we report high-resolution X-ray crystal structures of V. cholerae OmpU and OmpT complemented with molecular dynamics simulations. While similar overall to other general porins, the channels of OmpU and OmpT have unusual constrictions that create narrower barriers for small-molecule permeation and change the internal electric fields of the channels. Together with electrophysiological and in vitro transport data, our results illuminate small-molecule uptake within the Vibrionaceae.
许多革兰氏阴性菌的外膜（OM）含有一般的孔蛋白，这些孔蛋白形成非特异性的大直径通道，用于扩散吸收细胞生长和功能所需的小分子。虽然肠杆菌科（例如大肠杆菌 OmpF 和 OmpC）的孔蛋白在结构和生化方面已经得到了广泛的研究，但在弧菌科中，它们的对应物却知之甚少。霍乱弧菌是霍乱的病原体，它有两种主要的孔蛋白 OmpU 和 OmpT，尽管它们对细菌很重要，但目前还没有关于它们的结构信息。在这里，我们报道了霍乱弧菌 OmpU 和 OmpT 的高分辨率 X 射线晶体结构，并结合了分子动力学模拟。虽然总体上与其他一般孔蛋白相似，但 OmpU 和 OmpT 的通道具有不寻常的收缩，为小分子渗透创造了更窄的障碍，并改变了通道的内部电场。结合电生理学和体外运输数据，我们的结果阐明了弧菌科中小分子的摄取。
