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
(2.8.1.1)
(Sequence Homologues) (PDB Homologues)
- Biological species
-
Azotobacter vinelandii (Bacteria)
- PDB
-
1e0c
- SULFURTRANSFERASE FROM AZOTOBACTER VINELANDII
(1.8 Å)
- Catalytic CATH Domains
-
3.40.250.10
(see all for 1e0c)
Enzyme Reaction (EC:2.8.1.1)
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 |
Chemical Components
References
- 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.
- 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.
- 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.
- 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.
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 |