Enterotoxin type B

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Enterotoxin type B
Identifiers
Organism Staphylococcus aureus
Symbol entB
UniProt P01552
Other data
Staphylococcal/Streptococcal toxin, N-terminal domain
PDB 1eu4 EBI.jpg
Crystal structure of the superantigen Spe-H (zinc bound) from Streptococcus pyogenes
Identifiers
Symbol Staphylococcal/Streptococcal toxin, N-terminal domain
Pfam PF01123
InterPro IPR006173
PROSITE PDOC00250
SCOP 1se3
SUPERFAMILY 1se3
Staphylococcal/Streptococcal toxin, beta-grasp domain
Identifiers
Symbol Stap_Strp_tox_C
Pfam PF02876
InterPro IPR006123
PROSITE PDOC00250
SCOP 1se3
SUPERFAMILY 1se3

In the field of molecular biology, enterotoxin type B, also known as Staphylococcal enterotoxin B (SEB), this is an enterotoxin produced by the gram-positive bacteria Staphylococcus aureus. It is a common cause of food poisoning, with severe diarrhea, 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 a superantigen, causing the immune system to release a large amount of cytokines that lead to significant inflammation.

The protein domain found in this bacteria causes infections due to its multiple antibiotic resistant nature.[3] Additionally, this protein is the causative agent of Toxic shock syndrome.

Function[edit]

The function of this protein is to facilitate the infection of the host organism. It is a virulence factor designed to induce pathogenesis[3] One of the major virulence exotoxins is the toxic shock syndrome toxin (TSST), which is secreted by the organism upon successful invasion. It causes a major inflammatory response in the host via superantigenic properties, and is the causative agent of toxic shock syndrome. It functions as a superantigen through activation of a significant fraction of T-cells (up to 20%) by cross-linking MHC class II molecules with T-cell receptors. TSST is a multisystem illness with several symptoms such as high fever, hypotension, dizziness, rash and peeling skin.[3]

Structure[edit]

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]

N-terminal domain[edit]

The N-terminal domain is also referred to as OB-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 an inflammatory response.[5]

The N-terminal domain contains regions involved in Major Histocompatibility Complex class II association. It is a five stranded beta barrel that forms an OB fold.[6][7][8]

C-terminal domain[edit]

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.

References[edit]

  1. ^ a b "eMedicine - CBRNE - Staphylococcal Enterotoxin B". eMedicine. Retrieved 2011-02-06. 
  2. ^ Nema V, Agrawal R, Kamboj DV, Goel AK, Singh L (June 2007). "Isolation and characterization of heat resistant enterotoxigenic Staphylococcus aureus from a food poisoning outbreak in Indian subcontinent". Int. J. Food Microbiol. 117 (1): 29–35. doi:10.1016/j.ijfoodmicro.2007.01.015. PMID 17477998. 
  3. ^ a b c Blomster-Hautamaa DA, Kreiswirth BN, Kornblum JS, Novick RP, Schlievert PM (November 1986). "The nucleotide and partial amino acid sequence of toxic shock syndrome toxin-1". J. Biol. Chem. 261 (33): 15783–6. PMID 3782090. 
  4. ^ Acharya KR, Papageorgiou AC, Tranter HS (1998). "Crystal structure of microbial superantigen staphylococcal enterotoxin B at 1.5 A resolution: implications for superantigen recognition by MHC class II molecules and T-cell receptors". J. Mol. Biol. 277 (1): 61–79. doi:10.1006/jmbi.1997.1577. PMID 9514739. 
  5. ^ Brosnahan AJ, Schlievert PM (December 2011). "Gram-positive bacterial superantigen outside-in signaling causes toxic shock syndrome". FEBS J. 278 (23): 4649–67. doi:10.1111/j.1742-4658.2011.08151.x. PMID 21535475. 
  6. ^ Prasad GS, Earhart CA, Murray DL, Novick RP, Schlievert PM, Ohlendorf DH (December 1993). "Structure of toxic shock syndrome toxin 1". Biochemistry 32 (50): 13761–6. doi:10.1021/bi00213a001. PMID 8268150. 
  7. ^ Acharya KR, Passalacqua EF, Jones EY, Harlos K, Stuart DI, Brehm RD, Tranter HS (January 1994). "Structural basis of superantigen action inferred from crystal structure of toxic-shock syndrome toxin-1". Nature 367 (6458): 94–7. doi:10.1038/367094a0. PMID 8107781. 
  8. ^ Prasad GS, Radhakrishnan R, Mitchell DT, Earhart CA, Dinges MM, Cook WJ, Schlievert PM, Ohlendorf DH (June 1997). "Refined structures of three crystal forms of toxic shock syndrome toxin-1 and of a tetramutant with reduced activity". Protein Sci. 6 (6): 1220–7. doi:10.1002/pro.5560060610. PMC 2143723. PMID 9194182. 

This article incorporates text from the public domain Pfam and InterPro IPR006123 This article incorporates text from the public domain Pfam and InterPro IPR006173