Summary: Type II heat-labile enterotoxin , B subunit (LT-IIB)
This is the Wikipedia entry entitled "Heat-labile enterotoxin family". More...
Does Pfam agree with the content of the Wikipedia entry ?
Editing Wikipedia articles
Before you edit for the first time
You should take a few minutes to view the following pages:
How your contribution will be recorded
Heat-labile enterotoxin family Edit Wikipedia article
|cholera holotoxin, crystal form 1|
|cholera toxin b-pentamer complexed with metanitrophenyl-alpha-d-galactose|
|escherichia coli heat labile enterotoxin type iib b-pentamer|
In molecular biology, the heat-labile enterotoxin family includes Escherichia coli heat-labile toxin and cholera toxin secreted by Vibrio cholerae. 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.
- 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): 890–918. 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): 665–78. PMID 8805549.
Type II heat-labile enterotoxin , B subunit (LT-IIB) Provide feedback
Family of B subunits from the type II heat-labile enterotoxin. The B subunits form a pentameric ring, which interacts with one A subunit. Thus, the structural arrangement of type I and type II heat-labile enterotoxins are very similar .
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR010503
These are B subunits from the type II heat-labile enterotoxin. The B subunits form a pentameric ring, which interacts with one A subunit. Thus, the structural arrangement of type I and type II heat-labile enterotoxins are very similar [PUBMED:8805549].
|Cellular component||extracellular region (GO:0005576)|
|Biological process||pathogenesis (GO:0009405)|
- the number of sequences which exhibit this architecture
a textual description of the architecture, e.g. Gla, EGF x 2, Trypsin.
This example describes an architecture with one
Gladomain, followed by two consecutive
EGFdomains, and finally a single
- the UniProt description of the protein sequence
- the number of residues in the sequence
- the Pfam graphic itself.
Loading domain graphics...
We make a range of alignments for each Pfam-A family:
- the curated alignment from which the HMM for the family is built
- the alignment generated by searching the sequence database using the HMM
- Representative Proteomes (RPs) at 15%, 35%, 55% and 75% co-membership thresholds
- alignment generated by searching the NCBI sequence database using the family HMM
- alignment generated by searching the metagenomics sequence database using the family HMM
You can see the alignments as HTML or in three different sequence viewers:
- Pfam viewer
- an HTML-based viewer that uses DAS to retrieve alignment fragments on request
1Cannot generate PP/Heatmap alignments for seeds; no PP data available
Key: available, not generated, — not available.
Format an alignment
If you find these logos useful in your own work, please consider citing the following article:
Note: You can also download the data file for the tree.
Curation and family details
|Seed source:||Pfam-B_61882 (release 9.0)|
|Number in seed:||2|
|Number in full:||7|
|Average length of the domain:||121.70 aa|
|Average identity of full alignment:||64 %|
|Average coverage of the sequence by the domain:||99.77 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||6|
|Download:||download the raw HMM for this family|
Weight segments by...
Change the size of the sunburst
selected sequences to HMM
a FASTA-format file
- 0 sequences
- 0 species
How the sunburst is generated
Colouring and labels
Anomalies in the taxonomy tree
Missing taxonomic levels
Unmapped species names
Too many species/sequences
The tree shows the occurrence of this domain across different species. More...
You can use the tree controls to manipulate how the interactive tree is displayed:
- show/hide the summary boxes
- highlight species that are represented in the seed alignment
- expand/collapse the tree or expand it to a given depth
- select a sub-tree or a set of species within the tree and view them graphically or as an alignment
- save a plain text representation of the tree
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 LT-IIB domain has been found. There are 15 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.
Loading structure mapping...