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.[1] CooA regulates the expression of carbon monoxide dehydrogenase, an enzyme that catalyzes the oxidation of CO to CO2. The most well-studied CooA homolog comes from Rhodospirillum rubrum (RrCooA), but the CooA homolog from Carboxydothermus hydrogenoformans (ChCooA) has been studied as well.[2] The main difference between these two CooA homologs is the ferric heme coordination. For RrCooA, 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.[3][4][5] For ChCooA, the heme iron is ligated by a histidine and the N-terminal amine in both the ferric and ferrous states.[6] For both homologs, CO displaces the amine ligand and activates the protein to bind to its target DNA sequence.[7][8] Several structures of CooA exist: RrCooA in the ferrous state (1FT9),[9] ChCooA in the ferrous, imidazole-bound state (2FMY),[10] and ChCooA in the ferrous, CO-bound state (2HKX).[11]
^T. Shimizu; D. Huang; F. Yan; M. Stranava; M. Bartosova; V. Fojtíková; M. Martínková (2015). "Gaseous O2, NO, and CO in Signal Transduction: Structure and Function Relationships of Heme-Based Gas Sensors and Heme-Redox Sensors". Chem. Rev. 115 (13): 6491–6533. doi:10.1021/acs.chemrev.5b00018. PMID26021768.
^G. P. Roberts; R. L. Kerby; H. Youn; M. Conrad (2005). "CooA, A Paradigm for Gas Sensing Regulatory Proteins". J. Inorg. Biochem. 99 (1): 280–92. doi:10.1016/j.jinorgbio.2004.10.032. PMID15598507.
^Shigetoshi Aono (2003). "Biochemical and Biophysical Properties of the CO-Sensing Transcriptional Activator CooA". Acc. Chem. Res. 36 (11): 825–31. doi:10.1021/ar020097p. PMID14622029.
