title: Characterization of a new LexA binding motif in the marine magnetotactic bacterium strain MC-1.
abstract: MC-1 is a marine, magnetotactic bacterium that is phylogenetically associated with the alpha subclass of the Proteobacteria and is the first and only magnetotactic coccus isolated in pure culture to date. By using a TBLASTN search, a lexA gene was identified in the published genome of MC-1; it was subsequently cloned, and the protein was purified to >90% purity. Results from reverse transcription-PCR analysis revealed that the MC-1 lexA gene comprises a single transcriptional unit with two open reading frames encoding proteins of unknown function and with a rumA-like gene, a homologue of the Escherichia coli umuD gene. Mobility shift assays revealed that this LexA protein specifically binds both to its own promoter and to that of the umuDC operon. However, MC-1 LexA does not bind to the promoter regions of other genes, such as recA and uvrA, that have been previously reported to be regulated by LexA in bacterial species belonging to the alpha subclass of the Proteobacteria: Site-directed mutagenesis of both the lexA and umuDC operator regions demonstrated that the sequence CCTN(10)AGG is the specific target motif for the MC-1 LexA protein.
authors.affiliation: Departament Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain. afernandez@cbm.uam.es
authors.forename: Antonio R
authors.initials: AR
authors.lastname: Fernández de Henestrosa
authors.forename: Jordi
authors.initials: J
authors.lastname: Cuñé
authors.forename: Gerard
authors.initials: G
authors.lastname: Mazón
authors.forename: Bradley L
authors.initials: BL
authors.lastname: Dubbels
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Bazylinski
authors.forename: Jordi
authors.initials: J
authors.lastname: Barbé
mesh_terms: D020561:Alphaproteobacteria / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D004259:DNA-Directed DNA Polymerase; D024202:Electrophoretic Mobility Shift Assay; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D008280:Magnetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009876:Operon; D011401:Promoter Regions, Genetic; D018085:Regulon; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004259:DNA-Directed DNA Polymerase; D029968:Escherichia coli Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein; C078202:UmuC protein, E coli; C055218:UmuD protein, E coli