Neisserial TonB-dependent outer-membrane proteins: detection, regulation and distribution of three putative candidates identified from the genome sequences

Microbiology. 2001 May;147(Pt 5):1277-1290. doi: 10.1099/00221287-147-5-1277.


Computer searches were carried out of the gonococcal and meningococcal genome databases for previously unknown members of the TonB-dependent family (Tdf) of outer-membrane receptor proteins. Seven putative non-contiguous genes were found and three of these (identified in gonococcal strain FA1090) were chosen for further study. Consensus motif analysis of the peptide sequences was consistent with the three genes encoding TonB-dependent receptors. In view of the five previously characterized TonB-dependent proteins of pathogenic neisseriae, the putative genes were labelled tdfF, tdfG and tdfH. TdfF had homology with the siderophore receptors FpvA of Pseudomonas aeruginosa and FhuE of Escherichia coli, whereas TdfG and TdfH had homology with the haemophore receptor HasR of Serratia marcescens. The aim of this project was to characterize these proteins and determine their expression, regulation, distribution and surface exposure. Strain surveys of iron-stressed commensal and pathogenic neisseriae revealed that TdfF is unlikely to be expressed, TdfG is expressed by gonococci only and that TdfH is expressed by both meningococci and gonococci. Expression of TdfH was unaffected by iron availability. Susceptibility of TdfH to cleavage by proteases in live gonococci was consistent with surface exposure of this protein. TdfH may function as a TonB-dependent receptor for a non-iron nutrient source. Furthermore, TdfH is worthy of future investigation as a potential meningococcal vaccine candidate as it is a highly conserved, widely distributed and surface-exposed outer-membrane protein.

Publication types

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

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Bacterial Outer Membrane Proteins / genetics*
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / metabolism*
  • Blotting, Western
  • Consensus Sequence
  • Escherichia coli Proteins*
  • Genome, Bacterial*
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Neisseria / genetics*
  • Neisseria / metabolism
  • Polymerase Chain Reaction
  • Protein Binding
  • Sequence Alignment
  • Sequence Analysis, Protein
  • Siderophores / metabolism


  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Escherichia coli Proteins
  • Membrane Proteins
  • Siderophores
  • TdfF protein, Neisseria
  • TdfG protein, Neisseria
  • TdfH protein, Neisseria
  • tonB protein, Bacteria
  • tonB protein, E coli

Associated data

  • GENBANK/AF227418