title: CfaD-dependent expression of a novel extracytoplasmic protein from enterotoxigenic Escherichia coli.
abstract: H10407 is a strain of enterotoxigenic Escherichia coli (ETEC) that utilizes CFA/I pili to adhere to surfaces of the small intestine, where it elaborates toxins that cause profuse watery diarrhea in humans. Expression of the CFA/I pilus is positively regulated at the level of transcription by CfaD, a member of the AraC/XylS family. DNase I footprinting revealed that the activator has two binding sites upstream of the pilus promoter cfaAp. One site extends from positions -23 to -56, and the other extends from positions -73 to -103 (numbering relative to the transcription start site of cfaAp). Additional CfaD binding sites were predicted within the genome of H10407 by computational analysis. Two of these sites lie upstream of a previously uncharacterized gene, cexE. In vitro DNase I footprinting confirmed that both sites are genuine binding sites, and cexEp::lacZ reporters demonstrated that CfaD is required for the expression of cexE in vivo. The amino terminus of CexE contains a secretory signal peptide that is removed during translocation across the cytoplasmic membrane through the general secretory pathway. These studies suggest that CexE may be a novel ETEC virulence factor because its expression is controlled by the virulence regulator CfaD, and its distribution is restricted to ETEC.
authors.affiliation: Department of Microbiology and Immunology, University of Miami Miller School of Medicine, P.O. Box 016960 (R-138), Miami, FL 33101, USA.
authors.forename: M Carolina
authors.initials: MC
authors.lastname: Pilonieta
authors.forename: Maria D
authors.initials: MD
authors.lastname: Bodero
authors.forename: George P
authors.initials: GP
authors.lastname: Munson
mesh_terms: D000942:Antigens, Bacterial / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D001665:Binding Sites; D001692:Biological Transport; D003593:Cytoplasm / Q000378:metabolism; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D054307:Enterotoxigenic Escherichia coli / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D036781:Fimbriae Proteins / Q000235:genetics* / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics
chemical_list: D000942:Antigens, Bacterial; C069375:CfaD protein, E coli; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins