Structural insights into outer membrane asymmetry maintenance in Gram-negative bacteria by MlaFEDB

Xiaodi Tang, Shenghai Chang, Wen Qiao, Qinghua Luo, Yuejia Chen, Zhiying Jia, James Coleman, Ke Zhang, Ting Wang, Zhibo Zhang, Changbin Zhang, Xiaofeng Zhu, Xiawei Wei, Changjiang Dong, Xing Zhang, Haohao Dong

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44 Citations (Scopus)


The highly asymmetric outer membrane of Gram-negative bacteria functions in the defense against cytotoxic substances, such as antibiotics. The Mla pathway maintains outer membrane lipid asymmetry by transporting phospholipids between the inner and outer membranes. It comprises six Mla proteins, MlaFEDBCA, including the ABC transporter MlaFEDB, which functions via an unknown mechanism. Here we determine cryo-EM structures of Escherichia coli MlaFEDB in an apo state and bound to phospholipid, ADP or AMP-PNP to a resolution of 3.3–4.1 Å and establish a proteoliposome-based transport system that includes MlaFEDB, MlaC and MlaA–OmpF to monitor the transport direction of phospholipids. In vitro transport assays and in vivo membrane permeability assays combined with mutagenesis identify functional residues that not only recognize and transport phospholipids but also regulate the activity and structural stability of the MlaFEDB complex. Our results provide mechanistic insights into the Mla pathway, which could aid antimicrobial drug development.

Original languageEnglish
Pages (from-to)81-91
Number of pages11
JournalNature Structural & Molecular Biology
Issue number1
Early online date16 Nov 2020
Publication statusPublished - 1 Jan 2021

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