CooA

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Carbon monoxide oxidation system transcription regulator CooA
Identifiers
Organism Rhodospirillum rubrum
SymbolcooA
UniProt P72322
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Structures Swiss-model
Domains InterPro

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]

Contents

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 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 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 palindromic target sequences in promoter DNA and thereby regulate genes involved in CO oxidation. [7] [8] [9]

Several structures of CooA have been solved, including:

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. ↑ Körner H, Sofia HJ, Zumft WG (December 2003). "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. doi: 10.1016/S0168-6445(03)00066-4 . PMID   14638413.
  2. ↑ Shimizu T, Huang D, Yan F, Stranava M, Bartosova M, Fojtíková V, et al. (July 2015). "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. doi:10.1021/acs.chemrev.5b00018. PMID   26021768.
  3. ↑ Shelver D, Thorsteinsson MV, Kerby RL, Chung SY, Roberts GP, Reynolds MF, et al. (March 1999). "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. doi:10.1021/bi982658j. PMID   10052937.
  4. ↑ Dhawan IK, Shelver D, Thorsteinsson MV, Roberts GP, Johnson MK (September 1999). "Probing the heme axial ligation in the CO-sensing CooA protein with magnetic circular dichroism spectroscopy". Biochemistry. 38 (39): 12805–12813. doi:10.1021/bi991303c. PMID   10504250.
  5. ↑ Clark RW, Youn H, Parks RB, Cherney MM, Roberts GP, Burstyn JN (November 2004). "Investigation of the role of the N-terminal proline, the distal heme ligand in the CO sensor CooA". Biochemistry. 43 (44): 14149–14160. doi:10.1021/bi0487948. PMID   15518565.
  6. ↑ Inagaki S, Masuda C, Akaishi T, Nakajima H, Yoshioka S, Ohta T, et al. (February 2005). "Spectroscopic and redox properties of a CooA homologue from Carboxydothermus hydrogenoformans". The Journal of Biological Chemistry. 280 (5): 3269–3274. doi: 10.1074/jbc.m409884200 . PMID   15537640.
  7. 1 2 Lanzilotta WN, Schuller DJ, Thorsteinsson MV, Kerby RL, Roberts GP, Poulos TL (October 2000). "Structure of the CO sensing transcription activator CooA". Nature Structural Biology. 7 (10): 876–880. doi:10.1038/82820. PMID   11017196. S2CID   26285016.
  8. 1 2 Komori H, Inagaki S, Yoshioka S, Aono S, Higuchi Y (March 2007). "Crystal structure of CO-sensing transcription activator CooA bound to exogenous ligand imidazole". Journal of Molecular Biology. 367 (3): 864–871. doi:10.1016/j.jmb.2007.01.043. PMID   17292914.
  9. ↑ Shelver D, Kerby RL, He Y, Roberts GP (October 1997). "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. doi:10.1073/pnas.94.21.11216. PMID   9326589.
  10. ↑ Borjigin M, Li H, Lanz ND, Kerby RL, Roberts GP, Poulos TL (March 2007). "Structure-based hypothesis on the activation of the CO-sensing transcription factor CooA". Acta Crystallographica. Section D, Biological Crystallography. 63 (Pt 3): 282–287. Bibcode:2007AcCrD..63..282B. doi:10.1107/S0907444906051638. PMID   17327664.
  11. ↑ Roberts GP, Kerby RL, Youn H, Conrad M (January 2005). "CooA, a paradigm for gas sensing regulatory proteins". Journal of Inorganic Biochemistry. 99 (1): 280–292. doi:10.1016/j.jinorgbio.2004.10.032. PMID   15598507.
  12. ↑ Aono S (November 2003). "Biochemical and biophysical properties of the CO-sensing transcriptional activator CooA". Accounts of Chemical Research. 36 (11): 825–831. doi:10.1021/ar020097p. PMID   14622029.
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