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Structure and Substrate Specificity of the Pyrococcal Coenzyme A Disulfide Reductases/Polysulfide Reductases (CoADR/Psr): Implications for S0-Based Respiration and a Sulfur-Dependent Antioxidant System in Pyrococcus
- Source :
- Biochemistry. 52:2764-2773
- Publication Year :
- 2013
- Publisher :
- American Chemical Society (ACS), 2013.
-
Abstract
- FAD and NAD(P)H-dependent coenzyme A disulfide reductases/polysulfide reductases (CoADR/Psr) have been proposed to be important for the reduction of sulfur and disulfides in the sulfur-reducing anaerobic hyperthermophiles Pyrococcus horikoshii and Pyrococcus furiosus; however, the form(s) of sulfur that the enzyme actually reduces are not clear. Here we determined the structure for the FAD- and coenzyme A-containing holoenzyme from P. horikoshii to 2.7 Å resolution and characterized its substrate specificity. The enzyme is relatively promiscuous and reduces a range of disulfide, persulfide, and polysulfide compounds. These results indicate that the likely in vivo substrates are NAD(P)H and di-, poly-, and persulfide derivatives of coenzyme A, although polysulfide itself is also efficiently reduced. The role of the enzyme in the reduction of elemental sulfur (S(8)) in situ is not, however, ruled out by these results, and the possible roles of this substrate are discussed. During aerobic persulfide reduction, rapid recycling of the persulfide substrate was observed, which is proposed to occur via sulfide oxidation by O(2) and/or H(2)O(2). As expected, this reaction disappears under anaerobic conditions and may explain observations by others that CoADR is not essential for S(0) respiration in Pyrococcus or Thermococcus but appears to participate in oxidative defense in the presence of S(0). When compared to the homologous Npsr enzyme from Shewanella loihica PV-4 and homologous enzymes known to reduce CoA disulfide, the phCoADR structure shows a relatively restricted substrate channel leading into the sulfur-reducing side of the FAD isoalloxazine ring, suggesting how this enzyme class may select for specific disulfide substrates.
- Subjects :
- Models, Molecular
Protein Conformation
Coenzyme A
chemistry.chemical_element
Sulfides
Crystallography, X-Ray
Biochemistry
Cofactor
Substrate Specificity
Pyrococcus horikoshii
chemistry.chemical_compound
Pyrococcus
Oxidoreductase
NADH, NADPH Oxidoreductases
chemistry.chemical_classification
biology
Chemistry
biology.organism_classification
Sulfur
Kinetics
biology.protein
Pyrococcus furiosus
NAD+ kinase
Oxidoreductases
Oxidation-Reduction
NADP
Subjects
Details
- ISSN :
- 15204995 and 00062960
- Volume :
- 52
- Database :
- OpenAIRE
- Journal :
- Biochemistry
- Accession number :
- edsair.doi.dedup.....6067b743331ef5db3ab6e0d9b1ee4218