Promoter analysis of the class 2 flagellar operons of Salmonella.
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.
Ikebe
T
T
Faculty of Applied Biological Science, Hiroshima University, Japan.
Iyoda
S
S
Kutsukake
K
K
D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D005407:Flagella / Q000235:genetics*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D012475:Salmonella / Q000235:genetics*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C087497:FlgA protein, Salmonella; C085668:FlhB protein, Bacteria; C489554:FliL protein, E coli; D008565:Membrane Proteins; C073764:fliE protein, E coli; C074426:FliL protein, Bacteria