RT Journal Article
SR Electronic
T1 Architecture of a lipid transport system for the bacterial outer membrane
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 064360
DO 10.1101/064360
A1 Damian C. Ekiert
A1 Gira Bhabha
A1 Garrett Greenan
A1 Sergey Ovchinnikov
A1 Jeffery S. Cox
A1 Ronald D. Vale
YR 2016
UL http://biorxiv.org/content/early/2016/07/18/064360.abstract
AB How phospholipids are trafficked between the bacterial inner and outer membranes through the intervening hydrophilic space of the periplasm is not known. Here we report that members of the mammalian cell entry (MCE) protein family, which were previously implicated in outer membrane function, form hexameric rings with a central hydrophobic channel that can mediate phospholipid transport. The E. coli MCE protein MlaD forms part of a large multi-protein complex in the inner membrane that includes an unconventional ABC transporter. MlaC, a soluble lipid-binding protein, interacts with MlaD and an outer membrane protein complex, suggesting that it ferries lipids between the two membranes. In contrast, the syringe-like architecture of a second E. coli MCE protein, PqiB, creates a continuous channel of sufficient length to potentially span the entire periplasmic space. This work reveals a system of highly conserved protein-based channels that translocate lipids between the inner and outer membranes of bacteria and some eukaryotic organelles.One Sentence Summary Structural characterization of a widely-conserved transport system suggests a new model for lipid trafficking in double-membraned bacteria and organelles.