Identification of an ATP-binding cassette transport system required for translocation of lipopolysaccharide O-antigen side-chains across the cytoplasmic membrane of Klebsiella pneumoniae serotype O1

Mol Microbiol. 1994 Nov;14(3):505-19. doi: 10.1111/j.1365-2958.1994.tb02185.x.


The rfbKpO1 gene cluster of Klebsiella pneumoniae O1 directs synthesis of the D-galactan I component of the lipopolysaccharide O-antigen. The first two genes in the rfbKpO1 cluster encode RfbAKpO1 and RfbBKpO1, with predicted sizes of 29.5 or 30.0 kDa and 27.4 kDa, respectively. RfbBKpO1 contains a consensus ATP-binding domain and shares homology with several proteins which function as ATP-binding components of cell surface polysaccharide transporters. RfbAKpO1 is predicted to be an integral membrane protein with five putative membrane-spanning domains and its transmembrane topology was confirmed by TnphoA mutagenesis. The hydropathy plot of RfbAKpO1 resembles KpsM, the transcytoplasmic membrane component of the capsular polysaccharide transporter from Escherichia coli K-1 and K-5. These relationships suggest that RfbAKpO1 and RfbBKpO1 belong to a family of two-component ABC (ATP-binding cassette) transporters. E. coli K-12 containing a plasmid carrying an rfbKpO1 gene cluster deleted in rfbAKpO1 and rfbBKpO1 expresses rough lipopolysaccharide molecules on its surface and accumulates cytoplasmic O-antigen. When RfbAKpO1 and RfbBKpO1 are supplied in trans by a compatible plasmid, O-polysaccharide transport is restored and smooth D-galactan I-substituted lipopolysaccharide is produced. RfbAKpO1 and RfbBKpO1 are, therefore, proposed to constitute a system required for transport of D-galactan I across the cytoplasmic membrane, where RfbAKpO1 represents the membrane-spanning translocator and RfbBKpO1 couples the energy of ATP hydrolysis ot the transport process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism*
  • Adenosine Triphosphate / metabolism
  • Amino Acid Sequence
  • Base Sequence
  • Biological Transport, Active
  • Carbohydrate Sequence
  • Cell Membrane / metabolism
  • Chromosome Mapping
  • Cloning, Molecular
  • Codon / genetics
  • DNA, Bacterial / genetics
  • Genes, Bacterial
  • Klebsiella pneumoniae / classification
  • Klebsiella pneumoniae / genetics
  • Klebsiella pneumoniae / metabolism*
  • Microscopy, Immunoelectron
  • Molecular Sequence Data
  • Multigene Family
  • O Antigens
  • Polysaccharides, Bacterial / chemistry
  • Polysaccharides, Bacterial / metabolism*
  • Sequence Homology, Amino Acid
  • Serotyping


  • ATP-Binding Cassette Transporters
  • Codon
  • DNA, Bacterial
  • O Antigens
  • Polysaccharides, Bacterial
  • Adenosine Triphosphate

Associated data

  • GENBANK/L31775