The Legionella IcmS-IcmW protein complex is important for Dot/Icm-mediated protein translocation

Mol Microbiol. 2005 Feb;55(3):912-26. doi: 10.1111/j.1365-2958.2004.04435.x.


The intracellular pathogen Legionella pneumophila can infect and replicate within macrophages of a human host. To establish infection, Legionella require the Dot/Icm secretion system to inject protein substrates directly into the host cell cytoplasm. The mechanism by which substrate proteins are engaged and translocated by the Dot/Icm system is not well understood. Here we show that two cytosolic components of the Dot/Icm secretion machinery, the proteins IcmS and IcmW, play an important role in substrate translocation. Biochemical analysis indicates that IcmS and IcmW form a stable protein complex. In Legionella, the IcmW protein is rapidly degraded in the absence of the IcmS protein. Substrate proteins translocated into mammalian host cells by the Dot/Icm system were identified using the IcmW protein as bait in a yeast two-hybrid screen. It was determined that the IcmS-IcmW complex interacts with these substrates and plays an important role in translocation of these proteins into mammalian cells. These data are consistent with the IcmS-IcmW complex being involved in the recognition and Dot/Icm-dependent translocation of substrate proteins during Legionella infection of host cells.

Publication types

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

MeSH terms

  • Acanthamoeba castellanii / microbiology
  • Animals
  • Bacterial Proteins / metabolism*
  • Carrier Proteins / metabolism*
  • Cricetinae
  • Female
  • Gene Expression Regulation, Bacterial*
  • Humans
  • Legionella pneumophila / genetics
  • Legionella pneumophila / metabolism
  • Legionella pneumophila / pathogenicity*
  • Macrophages / microbiology
  • Mice
  • Molecular Sequence Data
  • Protein Transport
  • Two-Hybrid System Techniques


  • Bacterial Proteins
  • Carrier Proteins

Associated data

  • GENBANK/AY693712
  • GENBANK/AY693713
  • GENBANK/AY693714