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Updated: Jan 23, 2026

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Evidence for phospholipid export from the bacterial inner membrane by the Mla ABC transport system

Gareth W Hughes1, Stephen C L Hall1, Claire S Laxton2

  • 1School of Biosciences, University of Birmingham, Birmingham, UK.

Nature Microbiology
|June 26, 2019
PubMed

Insights

The Mla pathway maintains the Gram-negative outer membrane. We found MlaC protein structure and showed MlaFEDB machinery exports phospholipids to MlaC, suggesting a role in lipid transport.

Area of Science:

  • Microbiology
  • Structural Biology
  • Cell Biology

Background:

  • The Mla pathway is crucial for maintaining the asymmetrical Gram-negative outer membrane.
  • This pathway involves the MlaA-OmpC/F complex (outer membrane), MlaC (periplasmic protein), and MlaFEDB complex (inner membrane).

Purpose of the Study:

  • To elucidate the structure of the MlaC protein in its apo conformation.
  • To investigate the mechanism of phospholipid transport within the Mla pathway.
  • To determine the role of the MlaFEDB complex in phospholipid export.

Main Methods:

  • Crystal structure determination of MlaC in its phospholipid-free closed apo conformation.
  • Biochemical assays to study phospholipid export by the MlaFEDB complex.

Main Results:

  • The crystal structure of MlaC revealed a pivoting β-sheet mechanism for phospholipid-binding pocket regulation.
  • Evidence was provided that the MlaFEDB machinery exports phospholipids to MlaC in the periplasm.
  • Phospholipid export via MlaD is independent of ATP hydrolysis.

Conclusions:

  • The Mla pathway possesses an apparatus for lipid export away from the inner membrane.
  • The findings suggest a potential role for the Mla pathway in anterograde phospholipid transport.
  • The structural insights into MlaC provide a basis for understanding its function in membrane maintenance.

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