Interaction of lipopolysaccharides at intermolecular sites of the periplasmic Lpt transport assembly

Sci Rep. 2017 Aug 29;7(1):9715. doi: 10.1038/s41598-017-10136-0.


Transport of lipopolysaccharides (LPS) to the surface of the outer membrane is essential for viability of Gram-negative bacteria. Periplasmic LptC and LptA proteins of the LPS transport system (Lpt) are responsible for LPS transfer between the Lpt inner and outer membrane complexes. Here, using a monomeric E. coli LptA mutant, we first show in vivo that a stable LptA oligomeric form is not strictly essential for bacteria. The LptC-LptA complex was characterized by a combination of SAXS and NMR methods and a low resolution model of the complex was determined. We were then able to observe interaction of LPS with LptC, the monomeric LptA mutant as well as with the LptC-LptA complex. A LptC-LPS complex was built based on NMR data in which the lipid moiety of the LPS is buried at the interface of the two β-jellyrolls of the LptC dimer. The selectivity of LPS for this intermolecular surface and the observation of such cavities at homo- or heteromolecular interfaces in LptC and LptA suggests that intermolecular sites are essential for binding LPS during its transport.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport
  • Intracellular Space
  • Lipopolysaccharides / metabolism*
  • Magnetic Resonance Spectroscopy
  • Models, Biological
  • Models, Molecular
  • Molecular Conformation
  • Periplasmic Proteins / metabolism*
  • Protein Binding
  • Structure-Activity Relationship


  • Lipopolysaccharides
  • Periplasmic Proteins