Cryo-EM structures of lipopolysaccharide transporter LptB2FGC in lipopolysaccharide or AMP-PNP-bound states reveal its transport mechanism

Tang, Xiaodi, Chang, Shenghai, Luo, Qinghua, Zhang, Zhengyu, Qiao, Wen, Xu, Caihuang, Zhang, Changbin, Niu, Yang, Yang, Wenxian, Wang, Ting, Zhang, Zhibo, Zhu, Xiaofeng, Wei, Xiawei, Dong, Changjiang, Zhang, Xing and Dong, Haohao (2019) Cryo-EM structures of lipopolysaccharide transporter LptB2FGC in lipopolysaccharide or AMP-PNP-bound states reveal its transport mechanism. Nature Communications, 10 (1). ISSN 2041-1723

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Abstract

Lipopolysaccharides (LPS) of Gram-negative bacteria are critical for the defence against cytotoxic substances and must be transported from the inner membrane (IM) to the outer membrane (OM) through a bridge formed by seven membrane proteins (LptBFGCADE). The IM component LptB2FG powers the process through a yet unclarified mechanism. Here we report three high-resolution cryo-EM structures of LptB2FG alone and complexed with LptC (LptB2FGC), trapped in either the LPS- or AMP-PNP-bound state. The structures reveal conformational changes between these states and substrate binding with or without LptC. We identify two functional transmembrane arginine-containing loops interacting with the bound AMP-PNP and elucidate allosteric communications between the domains. AMP-PNP binding induces an inward rotation and shift of the transmembrane helices of LptFG and LptC to tighten the cavity, with the closure of two lateral gates, to eventually expel LPS into the bridge. Functional assays reveal the functionality of the LptF and LptG periplasmic domains. Our findings shed light on the LPS transport mechanism.

Item Type: Article
Uncontrolled Keywords: chemistry(all),biochemistry, genetics and molecular biology(all),physics and astronomy(all) ,/dk/atira/pure/subjectarea/asjc/1600
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
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Depositing User: LivePure Connector
Date Deposited: 27 Sep 2019 09:30
Last Modified: 01 Nov 2020 00:52
URI: https://ueaeprints.uea.ac.uk/id/eprint/72406
DOI: 10.1038/s41467-019-11977-1

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