Molecular Genetics and Genomics

, Volume 273, Issue 2, pp 197–206 | Cite as

Proteomic analysis reveals the wide-ranging effects of the novel, iron-responsive regulator RirA in Rhizobium leguminosarum bv. viciae

  • Jonathan D. Todd
  • Gary Sawers
  • Andrew W. B. Johnston
Original Paper


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 sufS2BCDS1XA 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.


Iron-responsive gene control Proteomics nifS RirA regulator Rhizobium suf genes 



The work was funded by the BBSRC. We thank F. Mulholland, C. Baker-Austin and M. Naldrett for help with proteomic analyses. We are grateful to Julian Parkhill and his colleagues at the Sanger Centre, Hinxton, for establishing the genome sequence of R. leguminosarum bv. viciae strain 3841


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Jonathan D. Todd
    • 1
  • Gary Sawers
    • 2
  • Andrew W. B. Johnston
    • 1
  1. 1.School of Biological SciencesUniversity of East AngliaNorwichUK
  2. 2.John Innes CentreNorwich Research ParkNorwichUK

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