title: Architectures of Lipid Transport Systems for the Bacterial Outer Membrane.
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.
authors.affiliation: 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.
authors.forename: Damian C
authors.initials: DC
authors.lastname: Ekiert
authors.affiliation: 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.
authors.forename: Gira
authors.initials: G
authors.lastname: Bhabha
authors.affiliation: Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Georgia L
authors.initials: GL
authors.lastname: Isom
authors.affiliation: 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.
authors.forename: Garrett
authors.initials: G
authors.lastname: Greenan
authors.affiliation: Institute for Protein Design, University of Washington, Seattle, WA 98195, USA.
authors.forename: Sergey
authors.initials: S
authors.lastname: Ovchinnikov
authors.affiliation: Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Henderson
authors.affiliation: Department of Microbiology and Immunology, The University of California, San Francisco, 600 16(th) Street, San Francisco, CA 94158, USA.
authors.forename: Jeffery S
authors.initials: JS
authors.lastname: Cox
authors.affiliation: 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.
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Vale
mesh_terms: D002462:Cell Membrane / Q000737:chemistry; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D008854:Microscopy, Electron; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C000620815:MlaD protein, E coli; D046912:Multiprotein Complexes; C000620816:YebT protein, E coli; C093588:pqi5 protein, E coli
keywords: E. coli; MCE; bacteria; cryo-EM; crystallography; hexametric rings; lipids; mammalian cell entry; outer membrane; periplasm; structure; transport