EC Number   |
General Information |
Reference  |
|---|
   1.8.4.2 | physiological function |
thiol-disulfide oxidoreductase, SdbA, in Streptococcus gordonii forms disulfide bonds in substrate proteins and plays a role in multiple phenotypes. SdbA has multiple redox partners, e.g. SdbB and CcdA2, forming a complex oxidative protein-folding pathway. This pathway is essential for autolysis, bacteriocin production, genetic competence, and extracellular DNA (eDNA) release in Streptococcus gordonii. These cellular processes are considered to be important for the success of Streptococcus gordonii as a dental plaque organism. Homologues of SdbA appear to be present in a range of Gram-positive bacteria that lack DsbA. SdbA is able to introduce a disulfide bond into its natural substrate, the major autolysin AtlS. This can be achieved with a single C-terminal cysteine in its CPDC active site, further suggesting SdbA is quite different from DsbA |
-, 765006 |
| 1.8.4.2 | malfunction |
SpeA in the culture supernatant remains reduced when gene sdbA is inactivated and restored to the oxidized state when a functional copy of sdbA is returned to the sdbA-knockout mutant. Complementation of sdbA deletion restores SpeA to an oxidized state. The enzyme mutant SdbAC49A forms a mixed disulfide with substrate mutant SpeAC87A. No reactions between SdbAC49A and SpeAC98A, SdbAC46A and SpeAC87A, or SdbAC46A and SpeAC98A |
765010 |
| 1.8.4.2 | physiological function |
SpyM18_2037, named SdbA, is the catalyst that introduces the disulfide bond in SpeA. Enzyme SdbA has a typical C46XXC49 active site motif commonly found in TDORs. The cysteines in the CXXC motif are required for the disulfide bond in SpeA to form. Interactions between SdbA and SpeA are examined using cysteine variant proteins. The results show that SdbAC49A forms a mixed disulfide with SpeAC87A, suggesting that the N-terminal Cys46 of SdbA and the C-terminal Cys98 of SpeA participate in the initial reaction. SpeA oxidized by SdbA displays biological activities suggesting that SpeA is properly folded following oxidation by SdbA. The enzyme substrate superantigen exotoxin A, SpeA (25 kDa) contains three cysteine residues (Cys87, Cys90, and Cys98). In the crystal structure of SpeA, Cys87 and Cys98 are linked by a disulfide bond. The disulfide bond and neighboring amino acids form a socalled disulfide loop, which is a conserved feature in all staphylococcal enterotoxins except the toxic shock syndrome toxin 1 (TSST-1). The importance of the disulfide bond in SpeA and staphylococcal enterotoxins (e.g. SEC2). SpeA and other streptococcal and staphylococcal superantigens are able to bind simultaneously to the major histocompatibility complex (MHC) class II molecules and the T-cell receptors, resulting in T cell activation and massive cytokine production |
765010 |
