title: RirA, an iron-responsive regulator in the symbiotic bacterium Rhizobium leguminosarum.
abstract: Mutations in a Rhizobium leguminosarum gene, rirA (rhizobial iron regulator), caused high-level, constitutive expression of at least eight operons whose transcription is normally Fe-responsive and whose products are involved in the synthesis or uptake of siderophores, or in the uptake of haem or of other iron sources. Close homologues of RirA exist in other rhizobia and in the pathogen Brucella; many other bacteria have deduced proteins with more limited sequence similarity. None of these homologues had been implicated in Fe-mediated gene regulation. Transcription of rirA itself is about twofold higher in cells grown in Fe-replete than in Fe-deficient growth media. Mutations in rirA reduced growth rates in Fe-replete and -depleted medium, but did not appear to affect symbiotic N(2) fixation.
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Todd
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
authors.forename: Margaret
authors.initials: M
authors.lastname: Wexler
authors.affiliation: Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK2.
authors.forename: Gary
authors.initials: G
authors.lastname: Sawers
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
authors.forename: Kay H
authors.initials: KH
authors.lastname: Yeoman
authors.affiliation: Department of Animal and Microbial Sciences, University of Reading, Reading RG6 6AJ, UK3.
authors.forename: Philip S
authors.initials: PS
authors.lastname: Poole
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
authors.forename: Andrew W B
authors.initials: AWB
authors.lastname: Johnston
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation; D009876:Operon; D011401:Promoter Regions, Genetic; D016961:Rhizobium leguminosarum / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D017262:Siderophores / Q000378:metabolism; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D017262:Siderophores; D007501:Iron