Summary: Peptidase family A21
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Peptidase family A21 Provide feedback
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External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR005313
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.
The asparagine endopeptidases are all autocatalytic endopeptidases utilizing Asn at position P1. Cleavage occurs as a consequence of cyclization of the Asn residue [PUBMED:16246842].
This group of peptidases belongs to the MEROPS family N2 (clan NA). In the Nudaurelia capensis omega virus capsid protein the residues that form the catalytic dyad in the active site are Glu103 and Asn570. The cleavage mediated by the enzyme is an autolytic one, and the catalytic Asn is also the P1 residue in the cleavage site, Asn570-|-Phe571 releasing a 74-residue fragment from the C terminus of the coat protein. This cleavage occurs during the late stages of virion assembly. Heterologous expression of the coat protein gene of tetravirus in a baculovirus system results in the spontaneous assembly of virus-like particles (VLPs) that remain uncleaved when purified at neutral pH [PUBMED:15659373].
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The clan contains a set of viral coat protein families and peptidase A6. The only known peptidase activity is an autolytic cleavage releasing a 44-residue C-terminal fragment. The reaction is very slow and only occurs within the assembled virion. There is debate whether this is actually a true peptidase. The virion with these coat or capsid proteins are icosahedral viruses containing sixty triangular coat protein units, each unit consisting of three proteins. The coat protein consists of two subdomains, an eight-stranded beta-barrel on the surface and a three-helix bundle on the inner face.
The clan contains the following 17 members:Birna_VP2 Bromo_coat Calici_coat Capsid-VNN Circo_capsid Como_LCP CRPV_capsid Cucumo_coat Luteo_coat Nepo_coat Peptidase_A21 Peptidase_A6 Rhv SP2 TT_ORF1 Tymo_coat Viral_coat
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:
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Curation and family details
|Number in seed:||5|
|Number in full:||29|
|Average length of the domain:||607.00 aa|
|Average identity of full alignment:||68 %|
|Average coverage of the sequence by the domain:||93.74 %|
|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:||8|
|Download:||download the raw HMM for this family|
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There is 1 interaction 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 Peptidase_A21 domain has been found. There are 20 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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