Summary

Cytosol aminopeptidase family, N-terminal domain

No Pfam abstract.

Literature references

Burley SK, David PR, Taylor A, Lipscomb WN; , Proc Natl Acad Sci U S A 1990;87:6878-6882.: Molecular structure of leucine aminopeptidase at 2.7-A resolution. PUBMED:2395881

InterPro entry IPR008283

Metalloproteases are the most diverse of the four main types of protease, with more than 50 families identified to date. In these enzymes, a divalent cation, usually zinc, activates the water molecule. The metal ion is held in place by amino acid ligands, usually three in number. The known metal ligands are His, Glu, Asp or Lys and at least one other residue is required for catalysis, which may play an electrophillic role. Of the known metalloproteases, around half contain an HEXXH motif, which has been shown in crystallographic studies to form part of the metal-binding site PUBMED:7674922. The HEXXH motif is relatively common, but can be more stringently defined for metalloproteases as 'abXHEbbHbc', where 'a' is most often valine or threonine and forms part of the S1' subsite in thermolysin and neprilysin, 'b' is an uncharged residue, and 'c' a hydrophobic residue. Proline is never found in this site, possibly because it would break the helical structure adopted by this motif in metalloproteases PUBMED:7674922.

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-, 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; 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 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.

This group of metallopeptidases belong to the MEROPS peptidase family M17 (leucyl aminopeptidase family, clan MF), the type example being leucyl aminopeptidase from Bos taurus (Bovine).

Aminopeptidases are exopeptidases involved in the processing and regular turnover of intracellular proteins, although their precise role in cellular metabolism is unclear PUBMED:1555602, PUBMED:2395881. Leucine aminopeptidases cleave leucine residues from the N-terminal of polypeptide chains, but substantial rates are evident for all amino acids PUBMED:2395881.

The enzymes exist as homo-hexamers, comprising 2 trimers stacked on top of one another PUBMED:2395881. Each monomer binds 2 zinc ions and folds into 2 alpha/beta-type quasi-spherical globular domains, producing a comma-like shape PUBMED:2395881. The N-terminal 150 residues form a 5-stranded beta-sheet with 4 parallel and 1 anti-parallel strand sandwiched between 4 alpha-helices PUBMED:2395881. An alpha-helix extends into the C-terminal domain, which comprises a central 8-stranded saddle-shaped beta-sheet sandwiched between groups of helices, forming the monomer hydrophobic core PUBMED:2395881. A 3-stranded beta-sheet resides on the surface of the monomer, where it interacts with other members of the hexamer PUBMED:2395881. The two zinc ions and the active site are entirely located in the C-terminal catalytic domain PUBMED:2395881.

Clan

This family is a member of clan MACRO (CL0223), which contains the following 2 members:

Macro Peptidase_M17_N

Gene Ontology

Cellular component	intracellular (GO:0005622)
Molecular function	aminopeptidase activity (GO:0004177)
Biological process	proteolysis (GO:0006508)

External database links

MEROPS:	M17
PANDIT:	PF02789
PROSITE:	PDOC00548
SCOP:	1lam
SYSTERS:	Peptidase_M17_N

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Alignments

There are various ways to view or download the sequence alignments that we store. You can use a sequence viewer to look at either the seed or full alignment for the family, or you can look at a plain text version of the sequence in a variety of different formats. More...

View options

Alignment:	Seed (103) Full (1440) NCBI (2158) Metagenomics (1036)
Viewer:

Formatting options

Alignment:	Seed (103) Full (1440)
Format:
Order:	Tree Alphabetical
Sequence:	Inserts lower case All upper case
Gaps:
Download/view:	Download View

Download options

Very large alignments can often cause problems for the formatting tool above. If you find that downloading or viewing a large alignment is problematic, you can also download a gzip-compressed, Stockholm-format file containing the seed or full alignment for this family.

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

The main seed and full alignments are generated using sequences from the UniProt sequence database. However, we also generate alignments using sequences from the NCBI sequence database and the "metaseq" metagenomics dataset.

You can view alignments from these two additional datasets using the form above, or you can download alignments of NCBI or metagenomics sequences, as gzip-compressed files.

Pfam alignments:	Seed (103) Full (1440) NCBI (2158) Metagenomics (1036)
Full length sequences	Full-sequences (1440)

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER2.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...

Trees

This page displays the phylogenetic tree for this family. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed or full alignments.

Note: You can also download the data files for the seed, full, NCBI or metagenomics trees.

Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation

Seed source:

Pfam-B_990 (release 3.0)

Previous IDs:

none

Type:

Domain

Author:

Bateman A, Griffiths-Jones SR

Number in seed:

103

Number in full:

1440

Average length of the domain:

123.70 aa

Average identity of full alignment:

21 %

Average coverage of the sequence by the domain:

24.91 %

HMM information

HMM build commands:

build method: hmmbuild -o /dev/null HMM SEED

search method: hmmsearch -Z 9421015 -E 1000 HMM pfamseq

Model details:

Parameter	Sequence	Domain
Gathering cut-off	20.8	20.8
Trusted cut-off	21.0	20.8
Noise cut-off	20.7	20.7

Model length:

125

Family (HMM) version:

10

Download:

download the raw HMM for this family

Species distribution

Tree controls

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The tree shows the occurrence of this domain across different species. More...

Species trees

We show the species tree in one of two ways. For smaller trees we try to show an interactive representation, which allows you to select specific nodes in the tree and view them as an alignment or as a set of Pfam domain graphics.

Unfortunately we have found that there are problems viewing the interactive tree when the it becomes larger than a certain limit. Furthermore, we have found that Internet Explorer can become unresponsive when viewing some trees, regardless of their size. We therefore show a text representation of the species tree when the size is above a certain limit or if you are using Internet Explorer to view the site.

If you are using IE you can still load the interactive tree by clicking the "Generate interactive tree" button, but please be aware of the potential problems that the interactive species tree can cause.

Interactive tree

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.

We also count the number of unique sequences on which each domain is found, which is shown in green. Note that a domain may appear multiple times on the same sequence, leading to the difference between these two numbers.

Finally, we group sequences from the same organism according to the NCBI code that is assigned by UniProt, allowing us to count the number of distinct sequences on which the domain is found. This value is shown in the pink boxes.

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.

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
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Interactions

There are 2 interactions for this family. More...

Peptidase_M17_N Peptidase_M17

Structures

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_M17_N domain has been found.

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Family: Peptidase_M17_N (PF02789)

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