Summary: Heat-labile enterotoxin beta chain
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Heat-labile enterotoxin family Edit Wikipedia article
|Heat-labile enterotoxin alpha chain|
cholera holotoxin, crystal form 1
|SCOPe||1lts / SUPFAM|
|Heat-labile enterotoxin beta chain|
cholera toxin b-pentamer complexed with metanitrophenyl-alpha-d-galactose
|SCOPe||1lts / SUPFAM|
|Type II heat-labile enterotoxin , B subunit (LT-IIB)|
escherichia coli heat labile enterotoxin type iib b-pentamer
|SCOPe||1tii / SUPFAM|
Elt is so named because it is inactivated at high temperatures.
The A subunit are transported inside by the pentameric B subunits. It then acts by raising cAMP levels through ADP-ribosylation of the alpha-subunit of a Gs protein leading to the constitutive activation of adenylate cyclase. Elevated cAMP levels stimulate the activation of the CFTR channel thus stimulating secretion of chloride ions and water from the enterocyte into the gut lumen. This ionic imbalance causes watery diarrhea.
In addition to its effects on chloride secretion, which involve the same steps as the effects of cholera toxin, Elt binds additional substrates: lipopolysaccharide on the surface of E. coli cells and A-type blood antigens. The importance of these binding events is not yet known.
These toxins consist of an AB5 multimer structure, in which a pentamer of B chains has a membrane-binding function and an A chain is needed for enzymatic activity. The B subunits are arranged as a doughnut-shaped pentamer, each subunit participating in ~30 hydrogen bonds and 6 salt bridges with its two neighbours.
The A subunit has a less well-defined secondary structure. It predominantly interacts with the pentamer via the C-terminal A2 fragment, which runs through the charged central pore of the B subunits. A putative catalytic residue in the A1 fragment (Glu112) lies close to a hydrophobic region, which packs two loops together. It is thought that this region might be important for catalysis and membrane translocation.
The cholera toxin is carried by the CTXÏ† bacteriophage and may be isolated from plamids. The E. coli LT (elt) is similarly associated with mobile elements, in this case Ent plasmids that can carry LT, ST, or both. Partial insertion sequences (ISs) flanking the elt genes provide extra transmission capabilities by homologous recombination at their inverted repeats. ÎŸÎ² phage-induced conversion in E. coli has been described as well.
- Glenn GM, Flyer DC, Ellingsworth LR, et al. (October 2007). "Transcutaneous immunization with heat-labile enterotoxin: development of a needle-free vaccine patch". Expert Rev Vaccines. 6 (5): 809â€“19. doi:10.1586/147605188.8.131.529. PMID 17931160.
- Mudrak B and Kuehn MJ (2010). "Heat-labile enterotoxin: Beyond GM1 binding". Toxins. 2 (6): 1445â€“1470. doi:10.3390/toxins2061445. PMC 3153253. PMID 22069646.
- Sixma TK, Kalk KH, van Zanten BA, Dauter Z, Kingma J, Witholt B, Hol WG (April 1993). "Refined structure of Escherichia coli heat-labile enterotoxin, a close relative of cholera toxin". J. Mol. Biol. 230 (3): 890â€“918. doi:10.1006/jmbi.1993.1209. PMID 8478941.
- van den Akker F, Sarfaty S, Twiddy EM, Connell TD, Holmes RK, Hol WG (June 1996). "Crystal structure of a new heat-labile enterotoxin, LT-IIb". Structure. 4 (6): 665â€“78. doi:10.1016/s0969-2126(96)00073-1. PMID 8805549.
- Schlor, S.; Riedl, S.; Bla, J.; Reidl, J. (1 January 2000). "Genetic Rearrangements of the Regions Adjacent to Genes Encoding Heat-Labile Enterotoxins (eltAB) of Enterotoxigenic Escherichia coli Strains". Applied and Environmental Microbiology. 66 (1): 352â€“358. doi:10.1128/AEM.66.1.352-358.2000. PMC 91829.
- Takeda, Y; Murphy, JR (January 1978). "Bacteriophage conversion of heat-labile enterotoxin in Escherichia coli". Journal of Bacteriology. 133 (1): 172â€“7. PMC 221991. PMID 338578.
- Pierre-HervÃ© Luppi. "The Discovery of Cholera-Toxin as a Powerful Neuroanatomical Tool". Retrieved 2011-03-23.
- Wagner B, Hufnagl K, Radauer C, et al. (April 2004). "Expression of the B subunit of the heat-labile enterotoxin of Escherichia coli in tobacco mosaic virus-infected Nicotiana benthamiana plants and its characterization as mucosal immunogen and adjuvant". Journal of Immunological Methods. 287 (1â€“2): 203â€“15. doi:10.1016/j.jim.2004.02.001. PMID 15099768.
- UniProtKB: Ctx , Elt-I , Elt-IIa , Elt-IIb
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Heat-labile enterotoxin beta chain Provide feedback
No Pfam abstract.
Sixma TK, Kalk KH, van Zanten BA, Dauter Z, Kingma J, Witholt B, Hol WG; , J Mol Biol 1993;230:890-918.: Refined structure of Escherichia coli heat-labile enterotoxin, a close relative of cholera toxin. PUBMED:8478941 EPMC:8478941
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR001835
Escherichia coli heat-labile enterotoxin is a bacterial protein toxin with an AB5 multimer structure, in which the B pentamer has a membrane-binding function and the A chain ( INTERPRO ) is needed for enzymatic activity [ PUBMED:8478941 ]. The B subunits are arranged as a donut-shaped pentamer, each subunit participating in ~30 hydrogen bonds and 6 salt bridges with its two neighbours [ PUBMED:8478941 ].
The A subunit has a less well-defined secondary structure. It predominantly interacts with the pentamer via the C-terminal A2 fragment, which runs through the charged central pore of the B subunits. A putative catalytic residue in the A1 fragment (Glu112) lies close to a hydrophobic region, which packs two loops together. It is thought that this region might be important for catalysis and membrane translocation [ PUBMED:8478941 ].
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Cellular component||extracellular region (GO:0005576)|
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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 9 members:Enterotoxin_b PatG_C PatG_D Pertus-S4-tox Pertus-S5-tox Pertussis_S2S3 SLT_beta SSL_OB Stap_Strp_toxin
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|Number in seed:||1|
|Number in full:||3|
|Average length of the domain:||102.00 aa|
|Average identity of full alignment:||99 %|
|Average coverage of the sequence by the domain:||82.26 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||21|
|Download:||download the raw HMM for this family|
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The tree shows the occurrence of this domain across different species. More...
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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 Enterotoxin_b domain has been found. There are 431 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 sequence.
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