Thiosulfate sulfurtransferase (prokaryotic)

 

Thiosulfate sulfurtransferase (rhodanese) is an ubiquitous enzyme that in vitro catalyses the transfer of a sulfur atom from suitable donors to nucleophilic acceptors by way of a double displacement mechanism. During the catalytic process the enzyme cycles between a sulfur-free and a persulfide-containing form, via formation of a persulfide linkage to a catalytic Cys residue.

 

Reference Protein and Structure

Sequence
P52197 UniProt (2.8.1.1) IPR001763 (Sequence Homologues) (PDB Homologues)
Biological species
Azotobacter vinelandii (Bacteria) Uniprot
PDB
1e0c - SULFURTRANSFERASE FROM AZOTOBACTER VINELANDII (1.8 Å) PDBe PDBsum 1e0c
Catalytic CATH Domains
3.40.250.10 CATHdb (see all for 1e0c)
Click To Show Structure

Enzyme Reaction (EC:2.8.1.1)

hydrogen cyanide
CHEBI:18407ChEBI
+
trioxidosulfanidosulfate(1-)
CHEBI:33542ChEBI
→
hydron
CHEBI:15378ChEBI
+
sulfite
CHEBI:17359ChEBI
+
thiocyanate
CHEBI:18022ChEBI
Alternative enzyme names: Rhodanase, Rhodanese, Thiosulfate cyanide transsulfurase, Thiosulfate thiotransferase,

Enzyme Mechanism

Introduction

Cys230, held in its thiolate form by the positively charged electrostatic field of the active site, attacks the thiosulfate substrate in a nucleophilic substitution reaction. The resulting persulfate bond is well stabilised by the active site eletrostatic field. Cyanate then binds and attacks the sulfonates cysteine residue (in a double displacement mechanism), resulting in the thiocyanate substrate and the regeneration of Cys230.

Catalytic Residues Roles

UniProt PDB* (1e0c)
Cys230 Css230A Acts as a catalytic nucleophile, and the resulting persulfide bond at the sulfydryl group is stabilised by the positive electostatic interactions. covalent catalysis
His234, Arg235 His234A, Arg235A The positively charged side chains contribute to active site electrostatic field, which interacts with the anionic substrate and creates hydrogen bonds to the persulfate at Cys 230 (Css 230). electrostatic stabiliser
Gln231 (main-N), Thr232 (main-N), His233 (main-N), Ser236 (main-N) Gln231A (main-N), Thr232A (main-N), His233A (main-N), Ser236A (main-N) The residue backbone NH is directed towards active pocket and the anionic substrate, allowing the formation of hydrogen bonds with the substrate as well as the persulfate residue. electrostatic stabiliser
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

References

  1. Bordo D et al. (2000), J Mol Biol, 298, 691-704. The crystal structure of a sulfurtransferase from Azotobacter vinelandii highlights the evolutionary relationship between the rhodanese and phosphatase enzyme families. DOI:10.1006/jmbi.2000.3651. PMID:10788330.
  2. Remelli W et al. (2012), PLoS One, 7, e45193-. Involvement of the Azotobacter vinelandii Rhodanese-Like Protein RhdA in the Glutathione Regeneration Pathway. DOI:10.1371/journal.pone.0045193. PMID:23049775.
  3. Pagani S et al. (2000), FEBS Lett, 472, 307-311. Mutagenic analysis of Thr-232 in rhodanese fromAzotobacter vinelandiihighlighted the differences of this prokaryotic enzyme from the known sulfurtransferases. DOI:10.1016/s0014-5793(00)01477-0.
  4. Gliubich F et al. (1996), J Biol Chem, 271, 21054-21061. Active site structural features for chemically modified forms of rhodanese. DOI:10.2210/pdb1ora/pdb. PMID:8702871.

Step 1.

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Catalytic Residues Roles

Residue Roles
Gln231A (main-N) electrostatic stabiliser
Thr232A (main-N) electrostatic stabiliser
His233A (main-N) electrostatic stabiliser
His234A electrostatic stabiliser
Arg235A electrostatic stabiliser
Ser236A (main-N) electrostatic stabiliser
Css230A covalent catalysis

Chemical Components

Step 1.

Contributors

James W. Murray, Craig Porter, Gemma L. Holliday