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Identification of a Salmonella virulence gene required for formation of filamentous structures containing lysosomal membrane glycoproteins within epithelial cells

Authors

  • Murry A. Stein,

    1. Biotechnology Laboratory, Room #237–6174 University Boulevard, and Departments of Biochemistry & Molecular Biology and Microbiology & Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
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  • Ka Yin Leung,

    1. Biotechnology Laboratory, Room #237–6174 University Boulevard, and Departments of Biochemistry & Molecular Biology and Microbiology & Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
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    • National University of Singapore, Department of Zoology, Faculty of Science, Lower Kent Ridge Road, Singapore, Thailand 0511.

  • Michael Zwick,

    1. Biotechnology Laboratory, Room #237–6174 University Boulevard, and Departments of Biochemistry & Molecular Biology and Microbiology & Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
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    • Institute of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada

  • Francisco Garcia-del Portillo,

    1. Biotechnology Laboratory, Room #237–6174 University Boulevard, and Departments of Biochemistry & Molecular Biology and Microbiology & Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
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    • §

      Departamento de Biologia Molecular, Centra de Biologia Molecular, Facultad de Biologia, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid, Spain.

  • B. Brett Finlay

    Corresponding author
    1. Biotechnology Laboratory, Room #237–6174 University Boulevard, and Departments of Biochemistry & Molecular Biology and Microbiology & Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
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summary

Salmonella species are facultative intracellular pathogens that invade epithelial cells and reside within lysosomal membrane glycoprotein (Igp)-containing vacuoles. Coincident with the onset of bacterial replication inside these vacuoles, Salmonella induce the formation of stable Igp-containing filamentous structures that connect with the Salmonella-containing vacuoles. Salmonella typhimurium SL1344::Tn 10dCm mutant strains unable to induce these structures were isolated. All contained insertions within a novel Salmonella induced filament gene A (sifA). sifA is present only in Salmonella species and encodes a protein with a predicted molecular mass of 38kDa and an apparent molecular mass of 35kDa. sifA is flanked by ∼300 base pairs, and sifA and its flanking DNA show no homology to sequences in DNA databases. sifA is located within the potABCD operon, a housekeeping locus involved in periplasmic transport of polyamines. Fourteen-base-pair direct repeats mark the probable site of integration of sifA and its flanking DNA at the 3 end of potB. sifA and its flanking DNA have a significantly reduced G+C content (41%) when compared with the potABCD operon (51%) and the Salmonella genome (52–54%). Deletion mutant strains

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