Mutations in Genes Downstream of the rpoN Gene (Encoding Sigma 54) of Klebsiella Pneumoniae Affect Expression From Sigma 54-dependent Promoters

Mol Microbiol. 1989 Dec;3(12):1765-75. doi: 10.1111/j.1365-2958.1989.tb00162.x.


Two open reading frames (ORFs), designated ORF95 and ORF162, downstream of the Klebsiella pneumoniae sigma 54 structural gene (rpoN) have been sequenced and shown to encode polypeptides of 12 kD and 16 kD, respectively. ORFs homologous to ORF95 are present downstream of four out of five rpoN genes sequenced to date from a range of Gram-negative bacteria, and ORF162 is also conserved, at least in Pseudomonas putida. Chromosomal mutations have been created in each gene using a kan cassette and both have the same phenotype, i.e. they cause an increase in the level of expression from sigma 54-dependent promoters. We propose that the products of both genes function to modulate the activity of E sigma 54, although a physiological role for these proteins has not yet been identified.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Chromosome Mapping
  • Codon
  • Gene Expression*
  • Genes*
  • Klebsiella pneumoniae / genetics*
  • Molecular Sequence Data
  • Mutation
  • Promoter Regions, Genetic*
  • Sigma Factor / genetics*
  • Transcription Factors / genetics*


  • Codon
  • Sigma Factor
  • Transcription Factors

Associated data

  • GENBANK/X16334
  • GENBANK/X16335