Unusual organization, complexity and redundancy at the Escherichia coli hcp-hcr operon promoter.
Expression from the Escherichia coli hcp-hcr operon promoter is optimally induced during anaerobic conditions in the presence of nitrite. This expression depends on transcription activation by FNR (fumarate and nitrate reduction regulator), which binds to a target centred at position -72.5 upstream of the transcript start site. Mutational analysis was exploited to identify the corresponding -10 and -35 hexamer elements. A DNA site for NarL and NarP, located at position -104.5, plays only a minor role, whereas NsrR binding to a DNA target centred at position +6 plays a major role in induction of the hcp-hcr operon promoter. Electrophoretic mobility-shift assays show that NsrR binds to this target. The consequences of this for the kinetics of induction of the hcp-hcr operon are discussed.
University of Birmingham, Edgbaston, UK.
David L
DL
Chismon
Douglas F
DF
Browning
Gregory K
GK
Farrant
Stephen J W
SJ
Busby
D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D048168:Escherichia coli K12 / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009876:Operon; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D009566:Nitrates; D009573:Nitrites; C529899:NsrR protein, E coli; D014157:Transcription Factors; C081466:narP protein, E coli; C069780:NarL protein, E coli