CooA
CooA is a heme-containing transcription factor that responds to the presence of carbon monoxide. It induces the expression of carbon monoxide dehydrogenase, which oxidizes CO. In the inactive ferric state, iron is bound to cysteine thiolate and the amine of an N-terminal proline, in addition to the N4 donor set of the porphyrinate. In the reduced state, an imidazole of histidine displaces the thiolate. The midpoint potential is -300 mV. In the presence of CO, the secondary amine ligand provided by proline is displaced from Fe. It is this CO-bound form that interacts with DNA.
