title: Iron-responsive gene expression in Pseudomonas fluorescens M114: cloning and characterization of a transcription-activating factor, PbrA.
abstract: In response to iron limitation. Pseudomonas fluorescens M114 induces a number of genes including an iron-scavenging siderophore termed pseudobactin M114, its cognate receptor, PbuA, and a casein protease. A Tn5lacZ-induced mutant (M114FA1) was isolated that exhibits a pleiotropic phenotype and lacks the ability to express these iron-regulated genes. A cosmid clone was identified which complements this mutation. This clone is capable of activating a number of iron-regulated promoter fusion constructs from P. fluorescens M114 and Pseudomonas putida WCS358 and can also promote expression of these fusions in Escherichia coli. A series of insertion mutants was constructed by homologous recombination which were unable to transcribe the promoter fusions. DNA sequence analysis of the complementing region identified one open reading frame (ORF) termed pbrA (pseudobactin regulation activation) and the deduced amino acid sequence shows domains with significant homology to a number of ECF (extracytoplasmic function) transcriptional regulators of the sigma 70 sigma factor family, including fecl required for expression of the ferric dicitrate outer-membrane receptor protein of E. coli. Sequences upstream of the pbrA gene suggest that transcription of pbrA may also be iron regulated.
authors.affiliation: Department of Microbiology, University College Cork, Ireland.
authors.forename: R
authors.initials: R
authors.lastname: Sexton
authors.forename: P R
authors.initials: PR
authors.lastname: Gill
authors.forename: M J
authors.initials: MJ
authors.lastname: Callanan
authors.forename: D J
authors.initials: DJ
authors.lastname: O'Sullivan
authors.forename: D N
authors.initials: DN
authors.lastname: Dowling
authors.forename: F
authors.initials: F
authors.lastname: O'Gara
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005798:Genes, Bacterial; D007501:Iron / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009842:Oligopeptides / Q000096:biosynthesis / Q000235:genetics; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011551:Pseudomonas fluorescens / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016415:Sequence Alignment; D017385:Sequence Homology; D015534:Trans-Activators / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D009842:Oligopeptides; C093496:PbrA protein, Pseudomonas fluorescens; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; C047631:pseudobactin receptor, Pseudomonas; C033038:pseudobactin; D007501:Iron