Conserved features of type III secretion

Cell Microbiol. 2004 Sep;6(9):805-16. doi: 10.1111/j.1462-5822.2004.00432.x.


Type III secretion systems (TTSSs) are essential mediators of the interaction of many Gram-negative bacteria with human, animal or plant hosts. Extensive sequence and functional similarities exist between components of TTSS from bacteria as diverse as animal and plant pathogens. Recent crystal structure determinations of TTSS proteins reveal extensive structural homologies and novel structural motifs and provide a basis on which protein interaction networks start to be drawn within the TTSSs, that are consistent with and help rationalize genetic and biochemical data. Such studies, along with electron microscopy, also established common architectural design and function among the TTSSs of plant and mammalian pathogens, as well as between the TTSS injectisome and the flagellum. Recent comparative genomic analysis, bioinformatic genome mining and genome-wide functional screening have revealed an unsuspected number of newly discovered effectors, especially in plant pathogens and uncovered a wider distribution of TTSS in pathogenic, symbiotic and commensal bacteria. Functional proteomics and analysis further reveals common themes in TTSS effector functions across phylogenetic host and pathogen boundaries. Based on advances in TTSS biology, new diagnostics, crop protection and drug development applications, as well as new cell biology research tools are beginning to emerge.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism*
  • Flagella / chemistry
  • Flagella / metabolism
  • Gram-Negative Bacteria / genetics*
  • Gram-Negative Bacteria / metabolism*
  • Gram-Negative Bacteria / pathogenicity
  • Models, Molecular
  • Molecular Chaperones / chemistry
  • Molecular Chaperones / metabolism
  • Molecular Sequence Data
  • Protein Binding
  • Protein Structure, Tertiary
  • Protein Transport*
  • Sequence Homology


  • Bacterial Proteins
  • Molecular Chaperones