An Unsuspected Autoregulatory Pathway Involving Apocytochrome TorC and Sensor TorS in Escherichia coli

Trimethylamine N-oxide (TMAO) respiration is carried out mainly by the Tor system in Escherichia coli. This system is encoded by the torCAD operon and comprises a periplasmic TMAO reductase (TorA) and a c-type cytochrome (TorC), which shuttles electrons to TorA. Expression of the tor operon is posit...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2001-09, Vol.98 (20), p.11615-11620
Main Authors: Gon, Stéphanie, Jourlin-Castelli, Cécile, Théraulaz, Laurence, Méjean, Vincent
Format: Article
Language:English
Subjects:
apocytochrome TorC
Apoproteins - genetics
Bacteria
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Bacterial Proteins - physiology
Biological Sciences
Cellular biology
Cloning, Molecular
Cytochrome c Group - genetics
Cytochrome c Group - metabolism
Cytochromes
Electrons
Escherichia coli
Escherichia coli - genetics
Escherichia coli - physiology
Escherichia coli Proteins
Kinetics
Operator regions
Operon
Operons
Periplasm
Phosphotransferases
Plasmids
Polymerase chain reaction
Protein Binding
Proteins
Sensors
Surface Plasmon Resonance
TorA gene
torA protein
TorC gene
TorC protein
torCAD gene
Torcs
TorD gene
torR protein
TorS protein
trimethylamine N-oxide
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Summary:Trimethylamine N-oxide (TMAO) respiration is carried out mainly by the Tor system in Escherichia coli. This system is encoded by the torCAD operon and comprises a periplasmic TMAO reductase (TorA) and a c-type cytochrome (TorC), which shuttles electrons to TorA. Expression of the tor operon is positively controlled by the TorS/TorR phosphorelay system in response to TMAO availability and negatively regulated by apocytochrome TorC. Interaction studies showed that, when immature, TorC can no longer bind TorA efficiently but can bind the periplasmic detector region of sensor TorS. ApoTorC negative autoregulation and TMAO induction are thus mediated by the same sensor protein. As apocytochromes related to TorC could not down-regulate the tor operon, we concluded that this negative control is highly specific. Moreover, the N-terminal half of apoTorC played no role in this control but the immature C-terminal domain of TorC strongly downregulated the tor operon and interacted with the TorS detector region. This sophisticated autoregulatory pathway thus involves the C-terminal domain of apoTorC and allows optimal TorC biogenesis by preventing from saturation the c-type cytochrome maturation machinery.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.211330598