Cryo-EM structures of a LptDE transporter in complex with Pro-macrobodies offer insight into lipopolysaccharide translocation

Nat Commun. 2022 Apr 5;13(1):1826. doi: 10.1038/s41467-022-29459-2.

Abstract

Lipopolysaccharides are major constituents of the extracellular leaflet in the bacterial outer membrane and form an effective physical barrier for environmental threats and for antibiotics in Gram-negative bacteria. The last step of LPS insertion via the Lpt pathway is mediated by the LptD/E protein complex. Detailed insights into the architecture of LptDE transporter complexes have been derived from X-ray crystallography. However, no structure of a laterally open LptD transporter, a transient state that occurs during LPS release, is available to date. Here, we report a cryo-EM structure of a partially opened LptDE transporter in complex with rigid chaperones derived from nanobodies, at 3.4 Å resolution. In addition, a subset of particles allows to model a structure of a laterally fully opened LptDE complex. Our work offers insights into the mechanism of LPS insertion, provides a structural framework for the development of antibiotics targeting LptD and describes a highly rigid chaperone scaffold to enable structural biology of challenging protein targets.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Outer Membrane Proteins / metabolism
  • Biological Transport
  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • Escherichia coli Proteins* / metabolism
  • Gram-Negative Bacteria / metabolism
  • Lipopolysaccharides* / metabolism

Substances

  • Bacterial Outer Membrane Proteins
  • Escherichia coli Proteins
  • Lipopolysaccharides