Two genes encoding a putative multidrug efflux pump of the RND/MFP family are cotranscribed with an rpoH gene in Bradyrhizobium japonicum

Gene. 2000 Jan 11;241(2):247-54. doi: 10.1016/s0378-1119(99)00490-4.


The rpoH3 gene of Bradyrhizobium japonicum codes for one of three sigma32-type transcription factors in this organism and is flanked by rag (rpoH3-associated) genes comprising the chromosomal arrangement ragABrpoH3ragCD. The first genes in this cluster code for a classical two-component regulatory system with an unknown function (Narberhaus et al., 1997. Mol. Microbiol. 24, 93-104). The deduced proteins of the last two genes display a high sequence similarity to heavy metal or multidrug efflux pumps of the RND (Resistance/Nodulation/cell Division)-MFP (Membrane Fusion Protein) family. Reverse transcription and polymerase chain reaction (RT-PCR) analysis demonstrated that ragC is cotranscribed with rpoH3. Mutant strains carrying disrupted rag genes or an extented deletion of the rag locus exhibited neither an apparent growth defect nor a deficiency in the symbiotic interaction with soybean roots. The minimal inhibitory concentrations (MICs) of various metals and organic compounds were identical for the wild-type and mutant strains. Moreover, translational lacZ fusions to each of the first four genes of the rag cluster showed a very low expression under all conditions tested; hence, the substrate for the putative efflux pump has not been uncovered.

MeSH terms

  • Bacterial Proteins / genetics*
  • Bradyrhizobium / genetics*
  • Bradyrhizobium / metabolism
  • Chromosome Mapping
  • Gene Expression
  • Genes, Bacterial
  • Membrane Proteins / genetics*
  • Multigene Family
  • Mutation
  • Phenotype
  • Transcription Factors / genetics*
  • Transcription, Genetic


  • Bacterial Proteins
  • Membrane Proteins
  • RpoH3 protein, Bradyrhizobium japonicum
  • Transcription Factors