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

Mol Microbiol. 1997 Mar;23(5):1063-73. doi: 10.1046/j.1365-2958.1997.2871652.x.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / immunology
  • Actins / metabolism
  • Amino Acid Sequence
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Proteins / analysis
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / immunology
  • Bacterial Proteins / metabolism*
  • Blotting, Southern
  • Cells, Cultured
  • Cloning, Molecular
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / immunology
  • DNA-Binding Proteins / metabolism*
  • Dysentery, Bacillary / genetics*
  • Escherichia coli / genetics
  • Escherichia coli Proteins*
  • Fluorescent Antibody Technique, Direct
  • Gene Expression Regulation, Bacterial
  • HeLa Cells
  • Humans
  • Hydrolases*
  • Molecular Sequence Data
  • Plasmids
  • Polymerase Chain Reaction
  • Recombination, Genetic
  • Shigella flexneri / genetics*
  • Transcription Factors / genetics*
  • Transcription Factors / immunology
  • Transcription Factors / metabolism*
  • Transcription, Genetic
  • Virulence / genetics


  • Actins
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Transcription Factors
  • virG protein, Shigella flexneri
  • OmpX protein, E coli
  • Hydrolases
  • SopA protein, Bacteria

Associated data

  • GENBANK/U73461