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Osmoporin OmpC forms a complex with MlaA to maintain outer membrane lipid asymmetry in Escherichia coli

Zhi-Soon Chong1, Wei-Fen Woo1, Shu-Sin Chng1,2

  • 1Department of Chemistry, National University of Singapore, Singapore, 117543.

Molecular Microbiology
|August 29, 2015
PubMed

Insights

The Mla system maintains bacterial outer membrane lipid asymmetry. This study reveals osmoporin OmpC is crucial for the Mla system

Area of Science:

  • Microbiology
  • Bacterial Cell Biology
  • Membrane Biophysics

Background:

  • Gram-negative bacteria possess an asymmetric outer membrane (OM) crucial for survival.
  • Lipid asymmetry, with phospholipids (PLs) in the inner leaflet and lipopolysaccharides (LPS) in the outer, prevents toxic compound entry.
  • Disruption of OM lipid asymmetry increases membrane permeability.

Purpose of the Study:

  • To elucidate the mechanism by which the multi-component Mla system maintains OM lipid asymmetry.
  • To investigate the role of osmoporin OmpC in the Mla system's function.

Main Methods:

  • Investigated the interaction between MlaA and OmpC/OmpF in Escherichia coli.
  • Assessed the localization of MlaA to the OM.
  • Analyzed the effect of OmpC or OmpF deletion on OM lipid asymmetry.

Main Results:

  • The OM lipoprotein MlaA specifically interacts with OmpC and OmpF.
  • OmpC, but not OmpF, is essential for maintaining OM lipid asymmetry.
  • Deletion of OmpC leads to PL accumulation in the outer leaflet, similar to MlaA mutants.

Conclusions:

  • Osmoporin OmpC is an integral component of the Mla system.
  • The OmpC-MlaA complex likely removes PLs from the outer leaflet to maintain OM lipid asymmetry.
  • OmpC has a novel function in lipid transport across the OM.

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