Lipopolysaccharides of polymyxin B-resistant mutants of Escherichia coli are extensively substituted by 2-aminoethyl pyrophosphate and contain aminoarabinose in lipid A

Mol Microbiol. 1995 Apr;16(2):271-8. doi: 10.1111/j.1365-2958.1995.tb02299.x.

Abstract

Lipopolysaccharides (LPS) of two polymyxin-resistant (pmr) mutants and the corresponding parent strain of Escherichia coli were chemically analysed for composition and subjected to 31P-NMR (nuclear magnetic resonance) for assessment of phosphate substitution. Whereas the saccharide portions, fatty acids, and phosphate contents were similar in wild-type and pmr LPS, the latter contained two- to threefold higher amounts of 2-aminoethanol. The pmr LPS also contained 4-amino-4-deoxy-L-arabinopyranose (L-Arap4N), which is normally not a component of E. coli LPS. This aminopentose has been assigned to be linked to the 4'-phosphate of lipid A. Comparative 31P-NMR analysis of the de-O-acylated LPS of the wild-type and pmr strains revealed that phosphate groups of the pmr LPS were mainly (71-79%) diphosphate diesters, which accounted for only 20% in the wild-type LPS. Diphosphate monoesters were virtually nonexistent in the pmr LPS, whereas they accounted for 42% of all phosphates in wild-type LPS. In the lipid A of the pmr strains, the 4'-phosphate was to a significant degree (35%) substituted by L-Arap4N, whereas in the wild-type LPS the L-ArapN was absent. In the pmr lipid A, 2-aminoethanol was completely substituting the glycosidic pyrophosphate but not the glycosidic monophosphate, forming a diphosphate diester linkage at this position in 40% of lipid A molecules. In the wild-type LPS the glycosidic position of lipid A carried mostly unsubstituted monophosphate and pyrophosphate. Thus the polymyxin resistance was shown to be associated, along with the esterification of the lipid A 4'-monophosphate by aminoarabinose, with extensive esterification of diphosphates in LPS by 2-aminoethanol.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Sugars / isolation & purification
  • Arabinose / analogs & derivatives*
  • Arabinose / chemistry
  • Arabinose / metabolism
  • Diphosphates / chemistry
  • Diphosphates / metabolism
  • Drug Resistance, Microbial
  • Escherichia coli / chemistry*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Ethanolamine
  • Ethanolamines / chemistry
  • Ethanolamines / metabolism
  • Lipid A / chemistry*
  • Lipid A / metabolism
  • Lipopolysaccharides / chemistry*
  • Lipopolysaccharides / metabolism
  • Magnetic Resonance Spectroscopy
  • Mutation
  • Phosphates / chemistry
  • Phosphates / metabolism
  • Polymyxin B / pharmacology*

Substances

  • Amino Sugars
  • Diphosphates
  • Ethanolamines
  • Lipid A
  • Lipopolysaccharides
  • Phosphates
  • aminoarabinose
  • 4-amino-4-deoxyarabinose
  • Ethanolamine
  • Arabinose
  • Polymyxin B