Promoter analysis of the class 2 flagellar operons of Salmonella

Tadayoshi Ikebe, Sunao Iyoda, Kazuhiro Kutsukake

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


The Salmonella flagellar operons are divided into three classes with reference to their relative positions in the transcriptional hierarchy. Expression of the class 2 operons requires the class 1 gene products, FlhD and FlhC, and is enhanced by an unknown mechanism in the presence of the class 3-specific sigma factor, FliA, and in the absence of its cognate anti- sigma factor, FlgM. In this study, the transcriptional start site mapping was performed by primer extension analysis for five class 2 operons, flgA, flgB, flhB, fliE and fliL. In all cases, one or a few major transcriptional start sites were identified. These start signals disappeared in the flhDC-mutant background, and their intensity decreased and increased in the fliA-mutant and flgM-mutant backgrounds, respectively. Therefore, we conclude that the FlhD/FlhC-dependent transcription is responsible for the FliA-dependent enhancement. Sequence comparison revealed that an imperfect inverted repetitious sequence is conserved upstream of the class 2 operons. Truncation of this sequence from the flgB promoter reduced its transcriptional activity to the background level, indicating that this is an essential cis-acting element for transcription of the class 2 operons.

Original languageEnglish
Pages (from-to)179-183
Number of pages5
JournalGenes and Genetic Systems
Issue number4
Publication statusPublished - Aug 1999

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics


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