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Enterotoxin type B

enterotoxin type b
In the field of molecular biology, enterotoxin type B, also known as Staphylococcal enterotoxin B SEB, 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 ingestion1 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 minutes1 Gastroenteritis occurs because SEB is a superantigen, causing the immune system to release a large amount of cytokines that lead to significant inflammation

Additionally, this protein is one of the causative agents of toxic shock syndrome


  • 1 Function
  • 2 Structure
    • 21 N-terminal domain
    • 22 C-terminal domain
  • 3 References


The function of this protein is to facilitate the infection of the host organism It is a virulence factor designed to induce pathogenesis3 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 skin3


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 modes when it interacts with MHC class II molecules or the T-cell receptor4

N-terminal domainedit

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 response5

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 fold678

C-terminal domainedit

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


  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 PMID 17477998 doi:101016/jijfoodmicro200701015 
  3. ^ a b 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 15 A resolution: implications for superantigen recognition by MHC class II molecules and T-cell receptors" J Mol Biol 277 1: 61–79 PMID 9514739 doi:101006/jmbi19971577 
  5. ^ Brosnahan AJ, Schlievert PM December 2011 "Gram-positive bacterial superantigen outside-in signaling causes toxic shock syndrome" FEBS J 278 23: 4649–67 PMC 3165073  PMID 21535475 doi:101111/j1742-4658201108151x 
  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 PMID 8268150 doi:101021/bi00213a001 
  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 PMID 8107781 doi:101038/367094a0 
  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 PMC 2143723  PMID 9194182 doi:101002/pro5560060610 

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

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