Function of the rfb gene cluster and the rfe gene in the synthesis of O antigen by Shigella dysenteriae 1

Mol Microbiol. 1993 Jul;9(2):393-402. doi: 10.1111/j.1365-2958.1993.tb01700.x.


A plasmid that included both an 8.9 kb chromosomal DNA insert containing genes from the rfb cluster of Shigella dysenteriae 1 and a smaller insert containing the rfp gene from a S. dysenteriae 1 multicopy plasmid resulted in efficient expression of O antigen in an rfb-deleted strain of Escherichia coli K-12. Eight genes were identified in the rfb fragment: the rfbB-CAD cluster which encodes dTDP-rhamnose synthesis, rfbX which encodes a hydrophobic protein involved in assembly of the O antigen, rfc which encodes the O antigen polymerase, and two sugar transferase genes. The production of an O antigen also required the E. coli K-12 rfe gene, which is known to encode a transferase which adds N-acetylglucosamine phosphate to the carrier lipid undecaprenol phosphate. Thus Rfe protein appears to function as an analogue of the Salmonella RfbP protein to provide the first sugar of the O unit. Functional analysis of the other genes was facilitated by the fact that partial O units of one, two or three sugars were efficiently transferred to the lipopolysaccharide core. This analysis indicated that the plasmid-encoded Rfp protein is the transferase that adds the second sugar of the O unit while the two rfb transferases add the distal sugars to make an O antigen whose structure is (Rha-Rha-Gal-GlcNAc)n. The use of the rfe gene product as the transferase that adds the first sugar of an O unit is a novel mechanism which may be used for the synthesis of other enteric O antigens.

Publication types

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

MeSH terms

  • Carbohydrate Metabolism
  • Carbohydrate Sequence
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial*
  • Glycosylation
  • Molecular Sequence Data
  • Multigene Family
  • O Antigens
  • Phenotype
  • Phylogeny
  • Plasmids
  • Polymorphism, Genetic
  • Polysaccharides, Bacterial / biosynthesis*
  • Salmonella typhimurium / genetics
  • Salmonella typhimurium / metabolism
  • Sequence Homology, Amino Acid
  • Shigella dysenteriae / genetics*
  • Shigella dysenteriae / immunology
  • Shigella dysenteriae / metabolism
  • Species Specificity
  • Transferases (Other Substituted Phosphate Groups) / genetics*
  • Transferases (Other Substituted Phosphate Groups) / metabolism


  • Escherichia coli Proteins
  • O Antigens
  • Polysaccharides, Bacterial
  • Transferases (Other Substituted Phosphate Groups)
  • wecA protein, E coli

Associated data

  • GENBANK/L07293