| Enterotoxin type B | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Organism | Staphylococcus aureus | ||||||
| Symbol | entB | ||||||
| UniProt | P01552 | ||||||
| |||||||
| Staphylococcal/Streptococcal toxin, N-terminal domain | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Crystal structure of the superantigen Spe-H (zinc bound) fromStreptococcus pyogenes | |||||||||
| Identifiers | |||||||||
| Symbol | Staphylococcal/Streptococcal toxin, N-terminal domain | ||||||||
| Pfam | PF01123 | ||||||||
| Pfam clan | CL0658 | ||||||||
| ECOD | 2.2.1 | ||||||||
| InterPro | IPR006173 | ||||||||
| PROSITE | PDOC00250 | ||||||||
| SCOP2 | 1se3 /SCOPe /SUPFAM | ||||||||
| |||||||||
| Staphylococcal/Streptococcal toxin, beta-grasp domain | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Stap_Strp_tox_C | ||||||||
| Pfam | PF02876 | ||||||||
| InterPro | IPR006123 | ||||||||
| PROSITE | PDOC00250 | ||||||||
| SCOP2 | 1se3 /SCOPe /SUPFAM | ||||||||
| |||||||||
In the field ofmolecular biology,enterotoxin type B, also known asStaphylococcal enterotoxin B (SEB), is anenterotoxin produced by thegram-positivebacteriaStaphylococcus aureus. It is a common cause offood poisoning, with severediarrhea,nausea and intestinal cramping often starting within a few hours of ingestion.[1] Being quite stable,[2] the toxin may remain active even after the contaminating bacteria are killed. It can withstand boiling at 100 °C for a few minutes.[1]Gastroenteritis occurs because SEB is asuperantigen, causing the immune system to release a large amount ofcytokines that lead to significant inflammation.
Additionally, this protein is one of the causative agents oftoxic shock syndrome.
The function of this protein is to facilitate the infection of thehost organism. It is avirulence factor designed to inducepathogenesis.[3] One of the major virulenceexotoxins is thetoxic shock syndrometoxin (TSST), which issecreted by theorganism upon successfulinvasion. It causes a majorinflammatory response in the host viasuperantigenic properties, and is the causative agent of toxic shock syndrome. It functions as a superantigen through activation of a significant fraction ofT-cells (up to 20%) by cross-linkingMHC class II molecules withT-cell receptors. TSST is a multisystem illness with severalsymptoms such as highfever,hypotension, dizziness, rash and peeling skin.[3]
All of these toxins share a similar two-domain fold (N and C-terminal domains) with a long alpha-helix in the middle of the molecule, a characteristic beta-barrel known as the "oligosaccharide/oligonucleotide fold" at the N-terminal domain and a beta-grasp motif at the C-terminal domain. Each superantigen possesses slightly different binding mode(s) when it interacts with MHC class II molecules or the T-cell receptor.[4]
TheN-terminal domain is also referred to asOB-fold, or in other words the oligonuclucleotide binding fold. This region contains a low-affinity major histocompatibility complex class II (MHC II) site which causes aninflammatory response.[5]
The N-terminaldomain contains regions involved in Major Histocompatibility Complex class II association. It is a five strandedbeta barrel that forms anOB fold.[6][7][8]
The beta-grasp domain has some structural similarities to the beta-grasp motif present in immunoglobulin-binding domains, ubiquitin, 2Fe-2 S ferredoxin and translation initiation factor 3 as identified by the SCOP database.
