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Overview for MACiE Entry M0320

Version history

General Information

EC Number: 1.8.5.- (A member of the Oxidoreductases, Acting on a sulfur group of donors, With a quinone or similar compound as acceptor)

Enzyme Name: sulfide:quinone oxidoreductase

Biological Species: Acidianus ambivalens (Archaea)

Catalytic Chain UniprotKB Accession Codes:

Representative PDB Code: 3h8i - THE FIRST X-RAY STRUCTURE OF A SULFIDE:QUINONEOXIDOREDUCTASE: INSIGHTS INTO SULFIDE OXIDATION MECHANISM (Resolution = 2.65 Å).

Catalytic CATH Codes:

  • Unassigned Domain

Display structure information

Overall Reaction:

Image of ubiquinone

Image of hydrogen sulfide

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Image of polysulfur chain

Image of ubiquinol

2 ubiquinone
C00399
CHEBI:16389
3 hydrogen sulfide
C00283
CHEBI:16136
polysulfur chain
X00147
2 ubiquinol
C00390
CHEBI:17976

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Stepwise Description of the Reaction

Step 1The substrate hydrogen sulfide is deprotonated by Asp353, activating the sulfur as a nucleophile towards the protein disulfide bridge.
Step 2The anionic Cys178A attacks the C4 position of FAD, initiating protonation of the N5 position.
Step 3The Cys350 dithiolate acts as a nucleophile towards the enzyme cofactor adduct, forming a three centre sulfur intermediate and the reduced form of FAD.
Step 4Ubiquinone, the physiological electron acceptor accepts a hydride from reduced FAD, regenerating the cofactor for the next round of sulfide oxidiation.
Step 5A second molecule of sulfide enters the active site and acts as a nucleophile towards the three member sulfur bridge between Cys178A and Cys350A.
Step 6The anionic Cys178A attacks the C4 position of FAD, initiating protonation of the N5 position.
Step 7The Cys350 dithiolate acts as a nucleophile towards the enzyme cofactor adduct, forming a three centre sulfur intermediate and the reduced form of FAD.
Step 8A second molecule of sulfide enters the active site and acts as a nucleophile towards the three member sulfur bridge between Cys178A and Cys350A.
Step 9Steric bulk brought about by the presence of an elongated sulfur chain directs the anionic Cys178A towards nucleophilic attack at Cys350A, reforming the active site disulfide bridge.
Step 10Ubiquinone, the physiological electron acceptor accepts a hydride from reduced FAD, regenerating the cofactor for the next round of sulfide oxidiation.

View similar reactions (composite manual annotation)


Catalytic Residues Involved

Type Number Chain Location of Function
Asp 215 A Side Chain
Asp 353 A Side Chain
Cys 178 A Side Chain
Cys 350 A Side Chain
Cys 129 A Side Chain
Lys 386 A Side Chain

Organic Cofactors for M0320

Type Identity Chain
FAD FAD 401 A Overview

References

  1. J. A. Brito et al. (2009), Biochemistry, 48, 5613-5622. Structural and functional insights into sulfide:quinone oxidoreductase.
    Medline: 19438211
  2. M. Marcia et al. (2009), Proc. Natl Acad. Sci. USA, 106, 9625-9830. The structure of Aquifex aeolicus sulfide:quinone oxidoreductase, a basis to understand sulfide detoxification and respiration.
    Medline: 19487671
  3. M. M. Cherney et al. (2010), J. Mol. Biol., 398, 292-305. Crystal structure of sulfide:quinone oxidoreductase from Acidithiobacillus ferrooxidans: insights into sulfidotrophic respiration and detoxification.
    Medline: 20303979

Homologue information for M0320 (3h8i)

MACiE Homologues (within the PDB)

MACiE Homologues (within UniprotKB/SwissProt)


Links to this entry in other databases

Link to EC-PDB-SUM Link to PDB-SUM Link to RCSB PDB Link to PDBe Link to CSA
Link to MetaCyc Link to KEGG Link to BRENDA Link to ExplorENZ

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nucleotide binding (molecular function)
NADH dehydrogenase activity (molecular function)
oxidoreductase activity (molecular function)
oxidation-reduction process (biological process)
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