Structural Basis for the Interaction of Lipopolysaccharide With Outer Membrane Protein H (OprH) From Pseudomonas Aeruginosa

J Biol Chem. 2011 Nov 11;286(45):39211-23. doi: 10.1074/jbc.M111.280933. Epub 2011 Aug 24.

Abstract

Pseudomonas aeruginosa is a major nosocomial pathogen that infects cystic fibrosis and immunocompromised patients. The impermeability of the P. aeruginosa outer membrane contributes substantially to the notorious antibiotic resistance of this human pathogen. This impermeability is partially imparted by the outer membrane protein H (OprH). Here we have solved the structure of OprH in a lipid environment by solution NMR. The structure reveals an eight-stranded β-barrel protein with four extracellular loops of unequal size. Fast time-scale dynamics measurements show that the extracellular loops are disordered and unstructured. It was previously suggested that the function of OprH is to provide increased stability to the outer membranes of P. aeruginosa by directly interacting with lipopolysaccharide (LPS) molecules. Using in vivo and in vitro biochemical assays, we show that OprH indeed interacts with LPS in P. aeruginosa outer membranes. Based upon NMR chemical shift perturbations observed upon the addition of LPS to OprH in lipid micelles, we conclude that the interaction is predominantly electrostatic and localized to charged regions near both rims of the barrel, but also through two conspicuous tyrosines in the middle of the bilayer. These results provide the first molecular structure of OprH and offer evidence for multiple interactions between OprH and LPS that likely contribute to the antibiotic resistance of P. aeruginosa.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / metabolism
  • Lipopolysaccharides / chemistry*
  • Lipopolysaccharides / metabolism
  • Micelles
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Pseudomonas aeruginosa / chemistry*
  • Pseudomonas aeruginosa / metabolism
  • Structure-Activity Relationship

Substances

  • Bacterial Outer Membrane Proteins
  • Lipopolysaccharides
  • Micelles
  • OprH protein, Pseudomonas aeruginosa

Associated data

  • PDB/2LHF