Multiple substrates of the Legionella pneumophila Dot/Icm system identified by interbacterial protein transfer
- Howard Hughes Medical Institute and Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Avenue, Boston, MA 02111
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Edited by John J. Mekalanos, Harvard Medical School, Boston, MA, and approved November 21, 2003 (received for review August 2, 2003)
Abstract
Legionella pneumophila is an intracellular pathogen that multiplies in a specialized vacuole within host cells. Biogenesis of this vacuole requires the Dot/Icm type IV protein translocation system. By using a Cre/loxP-based protein translocation assay, we found that proteins translocated by the Dot/Icm complex across the host phagosomal membrane can also be transferred from one bacterial cell to another. The flexibility of this system allowed the identification of several families of proteins translocated by the Dot/Icm complex. When analyzed by immunofluorescence microscopy, a protein identified by this procedure, SidC, was shown to translocate across the phagosomal membranes to the cytoplasmic face of the L. pneumophila phagosome. The identification of large numbers of these substrates, and the fact that the absence of any one substrate rarely results in strong defects in intracellular growth, indicate that there is significant functional redundancy among the Dot/Icm translocation targets.
Footnotes
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↵ * To whom correspondence should be addressed. E-mail: ralph.isberg{at}tufts.edu.
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This paper was submitted directly (Track II) to the PNAS office.
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Abbreviations: TFSS, type IV secretion systems; Sid, substrate of Icm/Dot transporter.
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Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession nos. AY504668–AY504685).
- Copyright © 2004, The National Academy of Sciences
