title: Identification and characterization of EspK, a type III secreted effector protein of enterohaemorrhagic Escherichia coli O157:H7.
abstract: Enterohaemorrhagic Escherichia coli (EHEC) causes bloody diarrhoea in humans and deploys a type III secretion system (T3SS) encoded by the locus of enterocyte effacement to elicit the formation of attaching and effacing (AE) lesions on intestinal epithelia. Here, we report the identification of a new secreted substrate of this system, z1829, which is encoded by cryptic prophage CP-933N. Elevated secretion of a beta-lactamase-z1829 fusion protein was detected upon mutation of sepD in EHEC O157:H7 and the fusion protein was translocated into infected epithelial cells in a T3SS-dependent manner; accordingly, we named the protein EspK. In common with the related Salmonella enterica type III secreted effector GogB, we observed that EspK localized to the cytoplasm when transiently expressed in COS-7 cells using EspK-specific antiserum. Inactivation of espK did not impair adherence or actin nucleation during infection of HeLa cells but affected persistence of EHEC O157:H7 in the intestines of orally inoculated calves. Inactivation of an orthologue of espK in the murine AE pathogen Citrobacter rodentium did not impair intestinal colonization in mice.
authors.affiliation: Division of Microbiology, Institute for Animal Health, Compton, Berkshire, UK.
authors.forename: Isabella
authors.initials: I
authors.lastname: Vlisidou
authors.forename: Olivier
authors.initials: O
authors.lastname: Marchés
authors.forename: Francis
authors.initials: F
authors.lastname: Dziva
authors.forename: Rosanna
authors.initials: R
authors.lastname: Mundy
authors.forename: Gad
authors.initials: G
authors.lastname: Frankel
authors.forename: Mark P
authors.initials: MP
authors.lastname: Stevens
mesh_terms: D000818:Animals; D019556:COS Cells; D002417:Cattle; D002522:Chlorocebus aethiops; D044082:Citrobacter rodentium / Q000737:chemistry / Q000235:genetics; D003593:Cytoplasm / Q000737:chemistry; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D004927:Escherichia coli Infections / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000737:chemistry / Q000235:genetics / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D044404:Genomic Islands; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D010750:Phosphoproteins / Q000235:genetics; D039002:Prophages / Q000235:genetics; D014162:Transfection; D037521:Virulence Factors
chemical_list: D029968:Escherichia coli Proteins; C515588:EspK protein, E coli; C457340:LEE protein, E coli; D010750:Phosphoproteins; D037521:Virulence Factors