SopA, the outer membrane protease responsible for polar localization of IcsA in Shigella flexneri

Authors

  • Coumaran Egile,

    1. Unité de Pathogénie Microbienne Moléculaire, Unité 389 Institut National de la Santé et de la Recherche Médicale, Institut Pasteur, 28 Rue du Docteur Roux, 75724 Paris Cédex 15, France.
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  • Hélène D’Hauteville,

    1. Unité de Pathogénie Microbienne Moléculaire, Unité 389 Institut National de la Santé et de la Recherche Médicale, Institut Pasteur, 28 Rue du Docteur Roux, 75724 Paris Cédex 15, France.
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  • Claude Parsot,

    1. Unité de Pathogénie Microbienne Moléculaire, Unité 389 Institut National de la Santé et de la Recherche Médicale, Institut Pasteur, 28 Rue du Docteur Roux, 75724 Paris Cédex 15, France.
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  • Philippe J. Sansonetti

    1. Unité de Pathogénie Microbienne Moléculaire, Unité 389 Institut National de la Santé et de la Recherche Médicale, Institut Pasteur, 28 Rue du Docteur Roux, 75724 Paris Cédex 15, France.
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Philippe J. Sansonetti E-mail psanson@pasteur. fr; Tel. (1) 45 68 83 42; Fax (1) 45 68 89 53.

Abstract

The spreading ability of Shigella flexneri, a facultative intracellular Gram-negative bacterium, within the host-cell cytoplasm is the result of directional assembly and accumulation of actin filaments at one pole of the bacterium. IcsA/VirG, the 120 kDa outer membrane protein that is required for intracellular motility, is located at the pole of the bacterium where actin polymerization occurs. Bacteria growing in laboratory media and within infected cells release a certain proportion of the surface-exposed IcsA after proteolytic cleavage. In this study, we report the characterization of the sopA gene which is located on the virulence plasmid and encodes the protein responsible for the cleavage of IcsA. The deduced amino acid sequence of SopA exhibits 60% identity with those of the OmpT and OmpP outer membrane proteases of Escherichia coli. The construction and phenotypic characterization of a sopA mutant demonstrated that SopA is required for exclusive polar localization of IcsA on the bacterial surface and proper expression of the motility phenotype in infected cells.

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