New members of the ctrA regulon: the major chemotaxis operon in Caulobacter is CtrA dependent.
The Caulobacter crescentus che promoter region consists of two divergent promoters, directing expression of the major chemotaxis operon and a novel gene cagA (chemotaxis associated gene A). Analyses of start sites by primer extension and alignment of the divergent promoters revealed significant similarities between them at the -35 promoter region. Both mcpA and cagA are differentially expressed in the cell cycle, with maximal activation of transcription in predivisional cells. The main difference between the mcpA and cagA promoters is that, in common with the fljK flagellin, cagA is expressed in swarmer cells. A cagA--lacZ promoter fusion that contains 36 bases of untranslated mRNA has sufficient information to segregate the lacZ transcript to swarmer cells. Expression of mcpA and cagA was dependent on DNA replication. Transcriptional epistasis experiments were performed to identify potential regulators in the flagellar hierarchy. The sigma factor RpoN, which is required for flagellar biogenesis, is not required for mcpA and cagA expression. Mutations in the genes for the MS-ring and the switch complex (flagellar class II mutants) do not affect expression of mcpA and cagA. However, CtrA, an essential response regulator of flagellar gene transcription, is required.
Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, UK1.
Susan E
SE
Jones
Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, UK1.
N L
NL
Ferguson
Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, UK1.
M R K
MRK
Alley
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D016934:Caulobacter / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D002633:Chemotaxis / Q000235:genetics*; D004268:DNA-Binding Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D005407:Flagella / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D000072236:Methyl-Accepting Chemotaxis Proteins; D008969:Molecular Sequence Data; D009876:Operon; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014157:Transcription Factors; D014158:Transcription, Genetic
D001426:Bacterial Proteins; C097706:CtrA protein, Caulobacter; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D014157:Transcription Factors