title: ToxR recognizes a direct repeat element in the toxT, ompU, ompT, and ctxA promoters of Vibrio cholerae to regulate transcription.
abstract: ToxR facilitates TcpP-mediated activation of the toxT promoter in Vibrio cholerae, initiating a regulatory cascade that culminates in cholera toxin secretion and toxin coregulated pilus expression. ToxR binds a region from -104 to -68 of the toxT promoter, from which ToxR recruits TcpP to the TcpP-binding site from -53 to -38. To precisely define the ToxR-binding site within the toxT promoter, promoter derivatives with single-base-pair transversions spanning the ToxR-footprinted region were tested for transcription activation and DNA binding. Nine transversions between -96 to -83 reduced toxT promoter activity 3-fold or greater, and all nine reduced the relative affinity of the toxT promoter for ToxR at least 2-fold, indicating that activation defects were due largely to reduced binding of ToxR to the toxT promoter. Nucleotides important for ToxR-dependent toxT activation revealed a consensus sequence of TNAAA-N(5)-TNAAA extending from -96 to -83, also present in other ToxR-regulated promoters. When these consensus nucleotides were mutated in the ompU, ompT, or ctxA promoters, ToxR-mediated regulation was disrupted. Thus, we have defined the core ToxR-binding site present in numerous ToxR-dependent promoters and we have precisely mapped the binding site for ToxR to a position three helical turns upstream of TcpP in the toxT promoter.
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Goss
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Morgan
authors.forename: Emily L
authors.initials: EL
authors.lastname: French
authors.forename: Eric S
authors.initials: ES
authors.lastname: Krukonis
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D018272:Porins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014734:Vibrio cholerae / Q000378:metabolism*
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C096349:OmpU protein, Vibrio cholerae; D018272:Porins; D014157:Transcription Factors; C405564:ompT protein, bacteria; C499324:toxR protein, Vibrio cholerae; C075626:tcpN protein, Vibrio cholerae