O2 -Sensing and O2 -dependent gene regulation in facultatively anaerobic bacteria

  • Unden G
  • Becker S
  • Bongaerts J
 et al. 
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Availability of O2 is one of the most important regulatory signals
in facultatively anaerobic bacteria. Various two- or one-component
sensor/regulator systems control the expression of aerobic and anaerobic
metabolism in response to O2. Most of the sensor proteins contain
heme or Fe as cofactors that interact with O2 either by binding or
by a redox reaction. The ArcA/ArcB regulator of aerobic metabolism
in Escherichia coli may use a different sensory mechanism. In two-component
regulators, the sensor is located in the cytoplasmic membrane, whereas
one-component regulators are located in the cytoplasm. Under most
conditions, O2 can readily reach the cytoplasm and could provide
the signal in the cytoplasm. The transcriptional regulator FNR of
E. Coli controls the expression of many genes required for anaerobic
metabolism in response to O2. Functional homologs of FNR are present
in facultatively anaerobic Proteobacteria and presumably also in
gram-positive bacteria. The target genes of FNR are mostly under
multiple regulation by FNR and other regulators that respond to O2,
nitrate, or glucose. FNR represents a 'one-component' sensor/regulator
and contains Fe for signal perception. In response to O2 availability,
FNR is converted reversibly from the aerobic (inactive) state to
the anaerobic (active) state. Experiments suggest that the Fe cofactor
is bound by four essential cysteine residues. The O2-triggered transformation
between active and inactive FNR presumably is due to a redox reaction
at the Fe cofactor, but other modes of interaction cannot be excluded.
O2 seems to affect the site-specific DNA binding of FNR at target
genes or the formation of an active transcriptional complex with
RNA polymerase.

Author-supplied keywords

  • Bacterial
  • Bacterial Proteins
  • Escherichia coli Proteins
  • Gene Expression Regulation
  • Gram-Negative Facultatively Anaerobic Rods
  • Iron-Sulfur Proteins
  • Oxygen
  • Transcription Factors

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  • G. Unden

  • S. Becker

  • J. Bongaerts

  • G. Holighaus

  • J. Schirawski

  • S. Six

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