CooA is a
heme-containing
transcription factor that responds to the presence of
carbon monoxide. This protein forms homodimers and is a homolog of
cAMP receptor protein. CooA regulates the expression of
carbon monoxide dehydrogenase
In enzymology, carbon monoxide dehydrogenase (CODH) () is an enzyme that catalyzes the chemical reaction
:CO + H2O + A \rightleftharpoons CO2 + AH2
The chemical process catalyzed by carbon monoxide dehydrogenase is similar to the water-gas shif ...
, an enzyme that catalyzes the oxidation of CO to CO
2. The most well-studied CooA homolog comes from ''
Rhodospirillum rubrum'' (''RrCooA),'' but the CooA homolog from ''
Carboxydothermus hydrogenoformans
''Carboxydothermus hydrogenoformans'' is an extremely thermophilic anaerobic Gram-positive bacterium that has the interesting property of producing hydrogen as a waste product while feeding on carbon monoxide and water. It also forms endospores. ...
'' (''Ch''CooA) has been studied as well. The main distinction between these two CooA homologs is the ferric heme coordination. For ''Rr''CooA, the ferric heme iron is bound to a cysteine and the amine of the N-terminal proline, while, in the ferrous state, a ligand switch occurs where a nearby histidine displaces the thiolate. For ''Ch''CooA, the heme iron is ligated by a histidine and the N-terminal amine in both the ferric and ferrous states. For both homologs, CO displaces the amine ligand and activates the protein to bind to its target DNA sequence. Several structures of CooA exist: RrCooA in the ferrous state (1FT9), ChCooA in the ferrous, imidazole-bound state (2FMY), and ChCooA in the ferrous, CO-bound state (2HKX).
References
{{DEFAULTSORT:Transcription Factor
Gene expression
Protein families
DNA
Gaseous signaling molecules