Summary

Papain family cysteine protease

No Pfam abstract.

InterPro entry IPR000668

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.

Cysteine peptidases have characteristic molecular topologies, which can be seen not only in their three-dimensional structures, but commonly also in the two-dimensional structures. These are peptidases in which the nucleophile is the sulphydryl group of a cysteine residue. Cysteine proteases are divided into clans (proteins which are evolutionary related), and further sub-divided into families, on the basis of the architecture of their catalytic dyad or triad PUBMED:11517925.

This group of proteins belong to the peptidase family C1, sub-family C1A (papain family, clan CA). It includes proteins classed as non-peptidase homologs. These are have either been shown experimentally to lack peptidase activity or lack one or more of the active site residues.

The papain family has a wide variety of activities, including broad-range (papain) and narrow-range endo-peptidases, aminopeptidases, dipeptidyl peptidases and enzymes with both exo- and endo-peptidase activity PUBMED:7845226. Members of the papain family are widespread, found in baculovirus PUBMED:8439290, eubacteria, yeast, and practically all protozoa, plants and mammals PUBMED:7845226. The proteins are typically lysosomal or secreted, and proteolytic cleavage of the propeptide is required for enzyme activation, although bleomycin hydrolase is cytosolic in fungi and mammals PUBMED:3117099. Papain-like cysteine proteinases are essentially synthesised as inactive proenzymes (zymogens) with N-terminal propeptide regions. The activation process of these enzymes includes the removal of propeptide regions. The propeptide regions serve a variety of functions in vivo and in vitro. The pro-region is required for the proper folding of the newly synthesised enzyme, the inactivation of the peptidase domain and stabilisation of the enzyme against denaturing at neutral to alkaline pH conditions. Amino acid residues within the pro-region mediate their membrane association, and play a role in the transport of the proenzyme to lysosomes. Among the most notable features of propeptides is their ability to inhibit the activity of their cognate enzymes and that certain propeptides exhibit high selectivity for inhibition of the peptidases from which they originate PUBMED:12188906.

The catalytic residues of papain are Cys-25 and His-159, other important residues being Gln-19, which helps form the 'oxyanion hole', and Asn-175, which orientates the imidazole ring of His-159.

Clan

This family is a member of clan Peptidase_CA (CL0125), which contains the following 44 members:

Acetyltransf_2 Amidase_5 CHAP DUF1175 DUF1287 DUF1460 DUF553 DUF830 DUF920 NLPC_P60 OTU Peptidase_C1 Peptidase_C10 Peptidase_C12 Peptidase_C16 Peptidase_C1_2 Peptidase_C2 Peptidase_C21 Peptidase_C23 Peptidase_C27 Peptidase_C28 Peptidase_C31 Peptidase_C32 Peptidase_C33 Peptidase_C34 Peptidase_C36 Peptidase_C39 Peptidase_C42 Peptidase_C47 Peptidase_C54 Peptidase_C58 Peptidase_C6 Peptidase_C65 Peptidase_C7 Peptidase_C70 Peptidase_C71 Peptidase_C78 Peptidase_C8 Peptidase_C9 Phytochelatin Rad4 Transglut_core UCH Viral_protease

Gene Ontology

Molecular function	cysteine-type peptidase activity (GO:0008234)
Biological process	proteolysis (GO:0006508)

External database links

HOMSTRAD:	cys
MEROPS:	C1
PANDIT:	PF00112
PRINTS:	PR00705
PROSITE:	PDOC00126
SCOP:	1aec
SYSTERS:	Peptidase_C1

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 (158) Full (3944) NCBI (5906) Metagenomics (474)
Viewer:

Formatting options

Alignment:	Seed (158) Full (3944)
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 (158) Full (3944) NCBI (5906) Metagenomics (474)
Full length sequences	Full-sequences (3944)

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:

Prosite

Previous IDs:

Cys-protease;

Type:

Domain

Author:

Sonnhammer ELL

Number in seed:

158

Number in full:

3944

Average length of the domain:

197.70 aa

Average identity of full alignment:

31 %

Average coverage of the sequence by the domain:

55.21 %

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	20.7	20.7
Trusted cut-off	20.7	20.7
Noise cut-off	20.6	20.6

Model length:

220

Family (HMM) version:

16

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
select a sub-tree or a set of species within the tree and view them graphically or as an alignment
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Interactions

There are 5 interactions for this family. More...

CathepsinC_exc Cystatin Chagasin_I42 Peptidase_C1 Inhibitor_I29

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 MSD 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_C1 domain has been found.

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Family: Peptidase_C1 (PF00112)

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