title: Functional analysis of lymphostatin homologues in enterohaemorrhagic Escherichia coli.
abstract: Enteropathogenic Escherichia coli contain a large chromosomal gene (lifA) that encodes lymphostatin, a predicted 365 kDa protein that inhibits the mitogen-activated proliferation of peripheral blood lymphocytes and lamina propria mononuclear cells and the synthesis of proinflammatory cytokines. Non-O157 serotypes of enterohaemorrhagic E. coli (EHEC) contain a highly homologous gene, designated efa1 (EHEC factor for adherence), which influences adherence to epithelial cells in vitro and intestinal colonization in calves. Serotype O157:H7 EHEC strains contain a truncated version of this gene (efa1') and a pO157-encoded homologue of lifA/efa1 (toxB). Here we report for the first time that efa1 inhibits mitogen-activated proliferation of bovine peripheral blood lymphocytes by EHEC O103:H2, but that E. coli K-12 strains expressing the N-terminal and central portions of the protein lack activity. While a Shiga toxin-negative E. coli O157:H7 strain was shown to possess lymphostatin-like activity, deletion of efa1' or toxB, singly or in combination, failed to significantly relieve the inhibitory effect.
authors.affiliation: Division of Microbiology, Institute for Animal Health, Compton Laboratory, Newbury, Berkshire, UK.
authors.forename: Abu-Bakr
authors.initials: AB
authors.lastname: Abu-Median
authors.forename: Pauline M
authors.initials: PM
authors.lastname: van Diemen
authors.forename: Francis
authors.initials: F
authors.lastname: Dziva
authors.forename: Isabella
authors.initials: I
authors.lastname: Vlisidou
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Wallis
authors.forename: Mark P
authors.initials: MP
authors.lastname: Stevens
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry; D002417:Cattle; D019453:Escherichia coli O157 / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D008213:Lymphocyte Activation; D017434:Protein Structure, Tertiary
chemical_list: D001427:Bacterial Toxins; C404907:Efa1 protein, E coli; D029968:Escherichia coli Proteins; C406587:lymphostatin protein, E coli