title: Proteomic analysis reveals the wide-ranging effects of the novel, iron-responsive regulator RirA in Rhizobium leguminosarum bv. viciae.
abstract: The wide-ranging effects of RirA, a novel Fe-responsive regulator of gene expression in Rhizobium leguminosarum bv. viciae, were monitored on 2D gels. Approximately 100 proteins were expressed at higher levels in a RirA(-) mutant, compared to wild type. These included the products of the sufS(2)BCDS(1)XA operon, which probably specifies the synthesis of [FeS] clusters. Using lac fusions, this operon was confirmed to be regulated by RirA in response to Fe availability. Genes for some ABC transporters, and a protein that may be involved in making a phenazine-like molecule, were also repressed by Fe in a RirA-dependent way. Strikingly, at least 17 proteins were reduced in abundance in the RirA(-) mutant. These included three ABC transporters, a GatB-like enzyme involved in tRNA modification, and a protein that may confer bacteriocin resistance. As judged by lac reporter fusions, this apparently positive control by RirA was probably due to post-transcriptional effects, in at least some cases. Therefore, although RirA shows no sequence similarity to Fur or DtxR, it functions as a wide-ranging, Fe-responsive regulator.
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Todd
authors.forename: Gary
authors.initials: G
authors.lastname: Sawers
authors.forename: Andrew W B
authors.initials: AW
authors.lastname: Johnston
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D017931:DNA Primers; D015180:Electrophoresis, Gel, Two-Dimensional; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism*; D035925:Iron-Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D040901:Proteomics; D016961:Rhizobium leguminosarum / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D035925:Iron-Regulatory Proteins; D007501:Iron