title: Enhanced secretion through the Shigella flexneri Mxi-Spa translocon leads to assembly of extracellular proteins into macromolecular structures.
abstract: Genes required for entry of Shigella flexneri into epithelial cells in vitro are clustered in two adjacent loci, one of which encodes secretory proteins, the IpaA-D proteins, and the other their dedicated secretion apparatus, the Mxi-Spa translocon. Ipa secretion, which is induced upon contact of bacteria with epithelial cells, is prevented during growth in vitro. Here, we show that ipaB and ipaD mutations lead to enhanced secretion of a set of about 15 proteins. These extracellular proteins and some Ipas associate in organized structures consisting of extended sheets. Growth of the wild-type strain in the presence of Congo red is shown to induce protein secretion through the Mxi-Spa translocon. Cultures grown to stationary phase in the presence of Congo red contain extracellular filaments whose composition and morphology are similar to those produced by the hypersecreting ipaB and ipaD mutants.
authors.affiliation: Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Parsot
authors.forename: R
authors.initials: R
authors.lastname: Ménard
authors.forename: P
authors.initials: P
authors.lastname: Gounon
authors.forename: P J
authors.initials: PJ
authors.lastname: Sansonetti
mesh_terms: D000942:Antigens, Bacterial / Q000096:biosynthesis / Q000235:genetics; D017209:Apoptosis; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D003224:Congo Red; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism / Q000648:ultrastructure; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D046911:Macromolecular Substances; D009154:Mutation; D010957:Plasmids; D012763:Shigella flexneri / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D014774:Virulence
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D016326:Extracellular Matrix Proteins; C063664:IpaA protein, Shigella flexneri; C095770:IpaD protein, Shigella flexneri; D046911:Macromolecular Substances; C087447:ipaB protein, Shigella; C092342:IpaC protein, Shigella; D003224:Congo Red