Supramolecular assemblies underpin turnover of outer membrane proteins in bacteria.
Supramolecular assemblies underpin turnover of outer membrane proteins in bacteria.
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DOI：
10.1038/nature14461
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发表时间：
2015-07-16
期刊：
影响因子：
64.8
通讯作者：
Kleanthous C
中科院分区：
文献类型：
--
作者：
Rassam P;Copeland NA;Birkholz O;Tóth C;Chavent M;Duncan AL;Cross SJ;Housden NG;Kaminska R;Seger U;Quinn DM;Garrod TJ;Sansom MS;Piehler J;Baumann CG;Kleanthous C
革兰氏阴性菌栖息在广泛的生态位。对于大肠杆菌来说，这包括河水以及人类和动物，在那里它既可以是细菌也可以是病原体。复杂的调控机制确保细菌具有正确的β-桶外膜蛋白（OMP）补充，以适应特定的栖息地。然而，没有机制是已知的替代外膜（OM），一个生物学之谜进一步混淆缺乏能源和高稳定性和丰富的外膜蛋白。在这里，我们揭示了过程的基础OMP营业额在E。大肠杆菌，并显示它是被动的和二元的性质，其中旧的外膜蛋白被取代的两极生长的细胞作为新的外膜蛋白取代它们的位置。使用荧光大肠杆菌素作为OMP特异性探针，结合整体和单分子荧光显微镜在体内和体外，以及分子动力学（MD）模拟，我们建立了二元OMP分配的机制。OMPs聚集形成直径约0.5 μm的岛，在那里它们的扩散受到与其他OMPs混杂相互作用的限制。OMP岛分布在整个细胞中，并含有Bam复合物，其催化OMP插入OM中。然而，OMP生物发生的梯度是最高的中细胞，但在细胞两极基本上不存在。累积效应是将旧的OMP岛推向生长细胞的两极，导致细胞分裂时的二元分布。因此，革兰氏阴性细菌的OM是一种空间和时间上有组织的结构，这种组织是OMP如何在膜中翻转的核心。
Gram-negative bacteria inhabit a broad range of ecological niches. For Escherichia coli, this includes river water as well as humans and animals where it can be both a commensal and a pathogen. Intricate regulatory mechanisms ensure bacteria have the right complement of β-barrel outer membrane proteins (OMPs) to enable adaptation to a particular habitat. Yet no mechanism is known for replacing OMPs in the outer membrane (OM), a biological enigma further confounded by the lack of an energy source and the high stability and abundance of OMPs. Here, we uncover the process underpinning OMP turnover in E. coli and show it to be passive and binary in nature wherein old OMPs are displaced to the poles of growing cells as new OMPs take their place. Using fluorescent colicins as OMP-specific probes, in combination with ensemble and single-molecule fluorescence microscopy in vivo and in vitro, as well as molecular dynamics (MD) simulations, we established the mechanism for binary OMP partitioning. OMPs clustered to form islands of ~0.5 μm diameter where their diffusion was restricted by promiscuous interactions with other OMPs. OMP islands were distributed throughout the cell and contained the Bam complex, which catalyses the insertion of OMPs in the OM. However, OMP biogenesis occurred as a gradient that was highest at mid-cell but largely absent at cell poles. The cumulative effect is to push old OMP islands towards the poles of growing cells, leading to a binary distribution when cells divide. Hence the OM of a Gram-negative bacterium is a spatially and temporally organised structure and this organisation lies at the heart of how OMPs are turned over in the membrane.