Thiosulfate sulfurtransferase (eukaryotic)

 

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
P00586 UniProt (2.8.1.1) IPR001763 (Sequence Homologues) (PDB Homologues)
Biological species
Bos taurus (Cattle) Uniprot
PDB
1rhs - SULFUR-SUBSTITUTED RHODANESE (1.36 Å) PDBe PDBsum 1rhs
Catalytic CATH Domains
3.40.250.10 CATHdb (see all for 1rhs)
Click To Show Structure

Enzyme Reaction (EC:2.8.1.1)

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

Enzyme Mechanism

Introduction

Cys247, 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 Cys247.

Catalytic Residues Roles

UniProt PDB* (1rhs)
Lys250, Arg187 Lys249A, Arg186A 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 247 (Css 247). electrostatic stabiliser
Gly251 (main-N), Val252 (main-N), Thr253 (main-N), Ser275 (main-N), Arg249 (main-N) Gly250A (main-N), Val251A (main-N), Thr252A (main-N), Ser274A (main-N), Arg248A (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. hydrogen bond donor, electrostatic stabiliser
Cys248 Cys247A Acts as a catalytic nucleophile, and the resulting persulfide bond at the sulfydryl group is stabilised by the positive electostatic interactions. nucleofuge, nucleophile
*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

bimolecular nucleophilic substitution, enzyme-substrate complex formation, enzyme-substrate complex cleavage, native state of enzyme regenerated

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. Salgado MPSC. (2005), J Mol Biol, 127, 149-162. Structural studies of RNA-dependent RNA polymerases. DOI:to delete. PMID:to delete.
  3. Cianci M et al. (2000), Biochim Biophys Acta, 1481, 103-108. Specific interaction of lipoate at the active site of rhodanese. PMID:11004580.
  4. Trevino RJ et al. (1999), J Biol Chem, 274, 13938-13947. NH2-terminal Sequence Truncation Decreases the Stability of Bovine Rhodanese, Minimally Perturbs Its Crystal Structure, and Enhances Interaction with GroEL under Native Conditions. DOI:10.1074/jbc.274.20.13938.
  5. 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.
  6. Luo GX et al. (1994), J Biol Chem, 269, 8220-8225. The sulfurtransferase activity and structure of rhodanese are affected by site-directed replacement of Arg-186 or Lys-249. PMID:8132546.
  7. Ploegman JH et al. (1979), J Mol Biol, 127, 149-162. The structure of bovine liver rhodanese. II. The active site in the sulfur-substituted and the sulfur-free enzyme. PMID:430559.

Step 1. The thiolate of Cys247 attacks the thiosulfate substrate in a nucleophilic substitution, resulting in the formation of the sulfite product an a sulfonated cysteine residue.

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Catalytic Residues Roles

Residue Roles
Arg186A hydrogen bond donor, electrostatic stabiliser
Arg248A (main-N) hydrogen bond donor, electrostatic stabiliser
Gly250A (main-N) hydrogen bond donor, electrostatic stabiliser
Val251A (main-N) hydrogen bond donor, electrostatic stabiliser
Thr252A (main-N) hydrogen bond donor, electrostatic stabiliser
Lys249A electrostatic stabiliser
Ser274A (main-N) electrostatic stabiliser
Cys247A nucleophile

Chemical Components

ingold: bimolecular nucleophilic substitution, enzyme-substrate complex formation

Step 2. The cyanate substrate attacks the sulfonated Cys247 in a nucleophilic substitution, resulting in the thiocyanate product and the regeneration of Cys247.

Download: Image, Marvin File

Catalytic Residues Roles

Residue Roles
Arg248A (main-N) hydrogen bond donor, electrostatic stabiliser
Gly250A (main-N) hydrogen bond donor, electrostatic stabiliser
Val251A (main-N) hydrogen bond donor, electrostatic stabiliser
Thr252A (main-N) hydrogen bond donor, electrostatic stabiliser
Arg186A electrostatic stabiliser
Lys249A electrostatic stabiliser
Ser274A (main-N) electrostatic stabiliser
Cys247A nucleofuge

Chemical Components

ingold: bimolecular nucleophilic substitution, enzyme-substrate complex cleavage, native state of enzyme regenerated
Download: Image, Marvin File

Step 1. The thiolate of Cys247 attacks the thiosulfate substrate in a nucleophilic substitution, resulting in the formation of the sulfite product an a sulfonated cysteine residue.

Step 2. The cyanate substrate attacks the sulfonated Cys247 in a nucleophilic substitution, resulting in the thiocyanate product and the regeneration of Cys247.

Products.

Contributors

Gemma L. Holliday, Daniel E. Almonacid, Christian Drew, Craig Porter