Summary: Assemblin (Peptidase family S21)
Assemblin (Peptidase family S21) Provide feedback
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Shieh HS, Kurumbail RG, Stevens AM, Stegeman RA, Sturman EJ, Pak JY, Wittwer AJ, Palmier MO, Wiegand RC, Holwerda BC, Stallings WC; , Nature 1996;383:279-282.: Three-dimensional structure of human cytomegalovirus protease. PUBMED:8805708 EPMC:8805708
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR001847
In the MEROPS database peptidases and peptidase homologues are grouped into clans and families. Clans are groups of families for which there is evidence of common ancestry based on a common structural fold:
- Each clan is identified with two letters, the first representing the catalytic type of the families included in the clan (with the letter 'P' being used for a clan containing families of more than one of the catalytic types serine, threonine and cysteine). Some families cannot yet be assigned to clans, and when a formal assignment is required, such a family is described as belonging to clan A-, C-, M-, N-, S-, T- or U-, according to the catalytic type. Some clans are divided into subclans because there is evidence of a very ancient divergence within the clan, for example MA(E), the gluzincins, and MA(M), the metzincins.
- Peptidase families are grouped by their catalytic type, the first character representing the catalytic type: A, aspartic; C, cysteine; G, glutamic acid; M, metallo; N, asparagine; S, serine; T, threonine; and U, unknown. The serine, threonine and cysteine peptidases utilise the amino acid as a nucleophile and form an acyl intermediate - these peptidases can also readily act as transferases. In the case of aspartic, glutamic and metallopeptidases, the nucleophile is an activated water molecule. In the case of the asparagine endopeptidases, the nucleophile is asparagine and all are self-processing endopeptidases.
In many instances the structural protein fold that characterises the clan or family may have lost its catalytic activity, yet retain its function in protein recognition and binding.
Proteolytic enzymes that exploit serine in their catalytic activity are ubiquitous, being found in viruses, bacteria and eukaryotes [PUBMED:7845208]. They include a wide range of peptidase activity, including exopeptidase, endopeptidase, oligopeptidase and omega-peptidase activity. Many families of serine protease have been identified, these being grouped into clans on the basis of structural similarity and other functional evidence [PUBMED:7845208]. Structures are known for members of the clans and the structures indicate that some appear to be totally unrelated, suggesting different evolutionary origins for the serine peptidases [PUBMED:7845208].
Not withstanding their different evolutionary origins, there are similarities in the reaction mechanisms of several peptidases. Chymotrypsin, subtilisin and carboxypeptidase C have a catalytic triad of serine, aspartate and histidine in common: serine acts as a nucleophile, aspartate as an electrophile, and histidine as a base [PUBMED:7845208]. The geometric orientations of the catalytic residues are similar between families, despite different protein folds [PUBMED:7845208]. The linear arrangements of the catalytic residues commonly reflect clan relationships. For example the catalytic triad in the chymotrypsin clan (PA) is ordered HDS, but is ordered DHS in the subtilisin clan (SB) and SDH in the carboxypeptidase clan (SC) [PUBMED:7845208, PUBMED:8439290].
This group of serine peptidases belong to MEROPS peptidase family S21 (assemblin family, clan 21).
A number of viral proteases have been discovered and their sequence similarity is very low. Studies with protease inhibitors suggest that the Herpesviridae protease is a serine protease belonging to either the trypsin-like or subtilisin-like families; it is not inhibited by inhibitors of Cys, Asp or metallo proteases.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Molecular function||serine-type endopeptidase activity (GO:0004252)|
|Biological process||proteolysis (GO:0006508)|
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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
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Curation and family details
|Seed source:||Pfam-B_729 (release 2.1)|
|Number in seed:||11|
|Number in full:||192|
|Average length of the domain:||280.20 aa|
|Average identity of full alignment:||30 %|
|Average coverage of the sequence by the domain:||49.47 %|
|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:||12|
|Download:||download the raw HMM for this family|
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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 Peptidase_S21 domain has been found. There are 47 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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