Biology:CooA

From HandWiki
Carbon monoxide oxidation system transcription regulator CooA
Crystallographic structure of the homodimeric RRcOOA (monomers colored cyan and green) bound to heme (spheres)
Identifiers
OrganismRhodospirillum rubrum
SymbolcooA
PDB1FT9 (ECOD)
UniProtP72322

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]

Homologs

The most well-studied CooA homolog comes from Rhodospirillum rubrum (RrCooA), but the homolog from Carboxydothermus hydrogenoformans (ChCooA) has also been characterized.[2]

The main structural difference between these homologs lies in ferric heme coordination. In RrCooA, the ferric heme iron is ligated by a cysteine and the amine of the N-terminal proline; in the ferrous state, a ligand switch occurs in which a histidine replaces the thiolate.[3][4][5] In contrast, ChCooA features histidine and the N-terminal amine as ligands in both ferric and ferrous states.[6]

Structure

CooA is a homodimeric, heme-containing transcription factor of the CAP/CRP family, with each monomer comprising an N-terminal heme-binding regulatory domain and a C-terminal helix-turn-helix motif that acts as a DNA-binding domain. The N-terminal domain coordinates a b-type heme whose axial ligands differ between species (for example, His-Pro versus His-His), and carbon monoxide (CO) binding to this heme triggers conformational changes that activate DNA binding. The two subunits associate through a coiled-coil-like interface, positioning the paired helix–turn–helix motifs to recognize target palindromic sequences in promoter DNA and thereby regulate genes involved in CO oxidation.[7][8][9]

Several structures of CooA have been solved, including:

  • RrCooA in the ferrous state (1FT9),[7]
  • ChCooA in the ferrous, imidazole-bound state (2FMY),[8]
  • ChCooA in the ferrous, CO-bound state (2HKX).[10]

Function

CooA responds to the presence of carbon monoxide and regulates the expression of carbon monoxide dehydrogenase, the enzyme that catalyzes the oxidation of CO to CO2.

For both RrCooA and ChCooA, CO displaces the amine ligand at the heme and activates the protein, enabling DNA binding at the target promoter sequence.[11][12]

References

  1. ↑ "Phylogeny of the bacterial superfamily of Crp-Fnr transcription regulators: exploiting the metabolic spectrum by controlling alternative gene programs". FEMS Microbiology Reviews 27 (5): 559–592. December 2003. doi:10.1016/S0168-6445(03)00066-4. PMID 14638413. 
  2. ↑ "Gaseous O2, NO, and CO in signal transduction: structure and function relationships of heme-based gas sensors and heme-redox sensors". Chemical Reviews 115 (13): 6491–6533. July 2015. doi:10.1021/acs.chemrev.5b00018. PMID 26021768. 
  3. ↑ "Identification of two important heme site residues (cysteine 75 and histidine 77) in CooA, the CO-sensing transcription factor of Rhodospirillum rubrum". Biochemistry 38 (9): 2669–2678. March 1999. doi:10.1021/bi982658j. PMID 10052937. 
  4. ↑ "Probing the heme axial ligation in the CO-sensing CooA protein with magnetic circular dichroism spectroscopy". Biochemistry 38 (39): 12805–12813. September 1999. doi:10.1021/bi991303c. PMID 10504250. 
  5. ↑ "Investigation of the role of the N-terminal proline, the distal heme ligand in the CO sensor CooA". Biochemistry 43 (44): 14149–14160. November 2004. doi:10.1021/bi0487948. PMID 15518565. 
  6. ↑ "Spectroscopic and redox properties of a CooA homologue from Carboxydothermus hydrogenoformans". The Journal of Biological Chemistry 280 (5): 3269–3274. February 2005. doi:10.1074/jbc.m409884200. PMID 15537640. 
  7. ↑ 7.0 7.1 "Structure of the CO sensing transcription activator CooA". Nature Structural Biology 7 (10): 876–880. October 2000. doi:10.1038/82820. PMID 11017196. 
  8. ↑ 8.0 8.1 "Crystal structure of CO-sensing transcription activator CooA bound to exogenous ligand imidazole". Journal of Molecular Biology 367 (3): 864–871. March 2007. doi:10.1016/j.jmb.2007.01.043. PMID 17292914. 
  9. ↑ "CooA, a CO-sensing transcription factor from Rhodospirillum rubrum, is a CO-binding heme protein". Proceedings of the National Academy of Sciences of the United States of America 94 (21): 11216–20. October 1997. doi:10.1073/pnas.94.21.11216. PMID 9326589. 
  10. ↑ "Structure-based hypothesis on the activation of the CO-sensing transcription factor CooA". Acta Crystallographica. Section D, Biological Crystallography 63 (Pt 3): 282–287. March 2007. doi:10.1107/S0907444906051638. PMID 17327664. Bibcode: 2007AcCrD..63..282B. 
  11. ↑ "CooA, a paradigm for gas sensing regulatory proteins". Journal of Inorganic Biochemistry 99 (1): 280–292. January 2005. doi:10.1016/j.jinorgbio.2004.10.032. PMID 15598507. 
  12. ↑ "Biochemical and biophysical properties of the CO-sensing transcriptional activator CooA". Accounts of Chemical Research 36 (11): 825–831. November 2003. doi:10.1021/ar020097p. PMID 14622029. 



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