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Cell. 2017 Apr 6;169(2):273-285.e17. doi: 10.1016/j.cell.2017.03.019.

Architectures of Lipid Transport Systems for the Bacterial Outer Membrane.

Author information

1
Department of Cellular and Molecular Pharmacology and the Howard Hughes Medical Institute, The University of California, San Francisco, 600 16(th) Street, San Francisco, CA 94158, USA; Department of Microbiology and Immunology, The University of California, San Francisco, 600 16(th) Street, San Francisco, CA 94158, USA. Electronic address: damian.ekiert@med.nyu.edu.
2
Department of Cellular and Molecular Pharmacology and the Howard Hughes Medical Institute, The University of California, San Francisco, 600 16(th) Street, San Francisco, CA 94158, USA.
3
Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK.
4
Institute for Protein Design, University of Washington, Seattle, WA 98195, USA.
5
Department of Microbiology and Immunology, The University of California, San Francisco, 600 16(th) Street, San Francisco, CA 94158, USA.

Abstract

How phospholipids are trafficked between the bacterial inner and outer membranes through the hydrophilic space of the periplasm is not known. We report that members of the mammalian cell entry (MCE) protein family form hexameric assemblies with a central channel capable of mediating lipid transport. The E. coli MCE protein, MlaD, forms a ring associated with an ABC transporter complex in the inner membrane. A soluble lipid-binding protein, MlaC, ferries lipids between MlaD and an outer membrane protein complex. In contrast, EM structures of two other E. coli MCE proteins show that YebT forms an elongated tube consisting of seven stacked MCE rings, and PqiB adopts a syringe-like architecture. Both YebT and PqiB create channels of sufficient length to span the periplasmic space. This work reveals diverse architectures of highly conserved protein-based channels implicated in the transport of lipids between the membranes of bacteria and some eukaryotic organelles.

KEYWORDS:

E. coli; MCE; bacteria; cryo-EM; crystallography; hexametric rings; lipids; mammalian cell entry; outer membrane; periplasm; structure; transport

PMID:
28388411
PMCID:
PMC5467742
DOI:
10.1016/j.cell.2017.03.019
[Indexed for MEDLINE]
Free PMC Article

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