Periplasmic Cleavage and Modification of the 1-phosphate Group of Helicobacter Pylori Lipid A

J Biol Chem. 2004 Dec 31;279(53):55780-91. doi: 10.1074/jbc.M406480200. Epub 2004 Oct 15.

Abstract

Pathogenic bacteria modify the lipid A portion of their lipopolysaccharide to help evade the host innate immune response. Modification of the negatively charged phosphate groups of lipid A aids in resistance to cationic antimicrobial peptides targeting the bacterial cell surface. The lipid A of Helicobacter pylori contains a phosphoethanolamine (pEtN) unit directly linked to the 1-position of the disaccharide backbone. This is in contrast to the pEtN units found in other pathogenic Gram-negative bacteria, which are attached to the lipid A phosphate group to form a pyrophosphate linkage. This study describes two enzymes involved in the periplasmic modification of the 1-phosphate group of H. pylori lipid A. By using an in vitro assay system, we demonstrate the presence of lipid A 1-phosphatase activity in membranes of H. pylori. In an attempt to identify genes encoding possible lipid A phosphatases, we cloned four putative orthologs of Escherichia coli pgpB, the phosphatidylglycerol-phosphate phosphatase, from H. pylori 26695. One of these orthologs, Hp0021, is the structural gene for the lipid A 1-phosphatase and is required for removal of the 1-phosphate group from mature lipid A in an in vitro assay system. Heterologous expression of Hp0021 in E. coli resulted in the highly selective removal of the 1-phosphate group from E. coli lipid A, as demonstrated by mass spectrometry. We also identified the structural gene for the H. pylori lipid A pEtN transferase (Hp0022). Mass spectrometric analysis of the lipid A isolated from E. coli expressing Hp0021 and Hp0022 shows the addition of a single pEtN group at the 1-position, confirming that Hp0022 is responsible for the addition of a pEtN unit at the 1-position in H. pylori lipid A. In summary, we demonstrate that modification of the 1-phosphate group of H. pylori lipid A requires two enzymatic steps.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry
  • Antimicrobial Cationic Peptides / chemistry
  • Bacterial Proteins / chemistry
  • Carbohydrate Sequence
  • Cell Membrane / metabolism
  • Cell-Free System
  • Cloning, Molecular
  • DNA / chemistry
  • Detergents / pharmacology
  • Escherichia coli / metabolism
  • Ethanolamines / chemistry
  • Genetic Vectors / metabolism
  • Genotype
  • Helicobacter pylori / metabolism*
  • Lipid A / chemistry*
  • Mass Spectrometry
  • Models, Biological
  • Models, Chemical
  • Molecular Sequence Data
  • Oligonucleotides / chemistry
  • Phosphates / chemistry
  • Phosphoric Monoester Hydrolases / chemistry
  • Promoter Regions, Genetic
  • Protein Conformation
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Substrate Specificity
  • Time Factors

Substances

  • ATP-Binding Cassette Transporters
  • Antimicrobial Cationic Peptides
  • Bacterial Proteins
  • Detergents
  • Ethanolamines
  • Lipid A
  • MsbA protein, Bacteria
  • Oligonucleotides
  • Phosphates
  • phosphorylethanolamine
  • DNA
  • Phosphoric Monoester Hydrolases