Summary: Staphylococcal/Streptococcal toxin, OB-fold domain
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This is the Wikipedia entry entitled "Enterotoxin type B". More...
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Enterotoxin type B Edit Wikipedia article
|Enterotoxin type B|
|Staphylococcal/Streptococcal toxin, N-terminal domain|
Crystal structure of the superantigen Spe-H (zinc bound) from Streptococcus pyogenes
|Symbol||Staphylococcal/Streptococcal toxin, N-terminal domain|
|Staphylococcal/Streptococcal toxin, beta-grasp domain|
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 ingestion. Being quite stable, the toxin may remain active even after the contaminating bacteria are killed. It can withstand boiling at 100 °C for a few minutes. 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.
The function of this protein is to facilitate the infection of the host organism. It is a virulence factor designed to induce pathogenesis. 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.
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.
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.
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.
- "eMedicine - CBRNE - Staphylococcal Enterotoxin B". eMedicine. Retrieved 2011-02-06.
- 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.
- 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.
- 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.
- 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. PMC . PMID 21535475.
- 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.
- 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.
- 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 . PMID 9194182.
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Staphylococcal/Streptococcal toxin, OB-fold domain Provide feedback
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External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR006173
Staphylococcus aureus is a Gram-positive coccus that grows in clusters or pairs, and is the major cause of nosocomial infections due to its multiple antibiotic resistant nature [PUBMED:3782090]. Patients who are immunocompromised (e.g., those suffering from third degree burns or chronic illness) are at risk from deep staphylococcal infections, such as osteomyelitis and pneumonia. Most skin infections are also caused by this bacterium.
Many virulence mechanisms are employed by Staphylococci to induce pathogenesis: these can include polysaccharide capsules and exotoxins [PUBMED:3782090]. One of the major virulence exotoxins is 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.
The structure of the TSST protein was originally determined to 2.5A by means of X-ray crystallography [PUBMED:8107781]. The N- and C-terminal domains both contain regions involved in MHC class II association; the C-terminal domain is also implicated in binding the T-cell receptor. Overall, the structure resembles that of Staphylococcal enterotoxin B (SEB), but differs in its N terminus and in the degree to which a long central helix is covered by surface loops [PUBMED:8268150]. The region around the carboxyl end of this helix is proposed to govern the superantigenic properties of TSST. An adjacent region along this helix is thought to be critical in the ability of TSST to induce toxic shock syndrome. Most recently, the structures of five mutants of TSST have been determined to 1.95A [PUBMED:9194182]. The mutations are in the central alpha-helix, and allow mapping of portions of TSST involved in superantigenicity and lethality.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Biological process||pathogenesis (GO:0009405)|
Below is a listing of the unique domain organisations or architectures in which this domain is found. More...
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This superfamily contains OB-fold domains found within bacterial enterotoxins. According to the SCOP and ECOD databases these domains are distinct from Clan:CL0021.
The clan contains the following 7 members:Enterotoxin_b Pertus-S4-tox Pertus-S5-tox Pertussis_S2S3 SLT_beta SSL_OB Stap_Strp_toxin
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1Cannot generate PP/Heatmap alignments for seeds; no PP data available
Key: available, not generated, — not available.
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|Author:||Finn RD, Bateman A, Griffiths-Jones SR|
|Number in seed:||5|
|Number in full:||8|
|Average length of the domain:||82.60 aa|
|Average identity of full alignment:||23 %|
|Average coverage of the sequence by the domain:||34.92 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 26740544 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||19|
|Download:||download the raw HMM for this family|
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The tree is built by looking at each sequence in the full alignment for the family. We take the name of the species given by UniProt and try to map that to the full taxonomic tree from NCBI. In some cases, the name chosen by UniProt does not map to any node in the NCBI tree, perhaps because the chosen name is listed as a synonym or a misspelling in the NCBI taxonomy.
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Since we reduce the species tree to only the eight main taxonomic levels, sequences that are mapped to the sub-species level in the tree would not normally be shown. Rather than leave out these species, we map them instead to their parent species. So, for example, for sequences belonging to one of the Vibrio cholerae sub-species in the NCBI taxonomy, we show them instead as belonging to the species Vibrio cholerae.
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The tree shows the occurrence of this domain across different species. More...
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For all of the domain matches in a full alignment, we count the number that are found on all sequences in the alignment. This total is shown in the purple box.
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We use the NCBI species tree to group organisms according to their taxonomy and this forms the structure of the displayed tree. Note that in some cases the trees are too large (have too many nodes) to allow us to build an interactive tree, but in most cases you can still view the tree in a plain text, non-interactive representation. Those species which are represented in the seed alignment for this domain are highlighted.
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There are 8 interactions for this family. More...
We determine these interactions using iPfam, which considers the interactions between residues in three-dimensional protein structures and maps those interactions back to Pfam families. You can find more information about the iPfam algorithm in the journal article that accompanies the website.
For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Stap_Strp_toxin domain has been found. There are 160 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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