Please note: this site relies heavily on the use of javascript. Without a javascript-enabled browser, this site will not function correctly. Please enable javascript and reload the page, or switch to a different browser.
108  structures 751  species 0  interactions 5251  sequences 390  architectures

Family: PKD_channel (PF08016)

Summary: Polycystin cation channel

Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.

The Pfam group coordinates the annotation of Pfam families in Wikipedia, but we have not yet assigned a Wikipedia article to this family. If you think that a particular Wikipedia article provides good annotation, please let us know.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

Polycystin cation channel Provide feedback

This family contains the cation channel region of PKD1 and PKD2 proteins.

Literature references

  1. Chen XZ, Vassilev PM, Basora N, Peng JB, Nomura H, Segal Y, Brown EM, Reeders ST, Hediger MA, Zhou J; , Nature 1999;401:383-386.: Polycystin-L is a calcium-regulated cation channel permeable to calcium ions. PUBMED:10517637 EPMC:10517637

  2. Vassilev PM, Guo L, Chen XZ, Segal Y, Peng JB, Basora N, Babakhanlou H, Cruger G, Kanazirska M, Ye Cp, Brown EM, Hediger MA, Zhou J; , Biochem Biophys Res Commun 2001;282:341-350.: Polycystin-2 is a novel cation channel implicated in defective intracellular Ca(2+) homeostasis in polycystic kidney disease. PUBMED:11264013 EPMC:11264013

Internal database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR013122

Polycystic kidney diseases (PKD) are disorders characterised by large numbers of cysts distributed throughout grossly-enlarged kidneys. Cyst development is associated with impairment of kidney function, and ultimately kidney failure and death [ PUBMED:8643665 ]. Most cases of autosomal dominant PKD result from mutations in the PKD1 gene that cause premature protein termination.

A second gene for autosomal dominant polycystic kidney disease has been identified by positional cloning [ PUBMED:8650545 ]. The predicted 968-amino acid sequence of the PKD2 gene product (polycystin-2) contains 6 transmembrane domains, with intracellular N- and C-termini. Polycystin-2 shares some similarity with the family of voltage-activated calcium (and sodium) channels, and contains a potential calcium-binding domain.

Polycystin-2 is strongly expressed in ovary, foetal and adult kidney, testis, and small intestine. Polycystin-1 requires the presence of this protein for stable expression and is believed to interact with it via its C terminus. All mutations between exons 1 and 11 result in a truncated polycystin-2 that lacks a calcium-binding EF-hand domain and the cytoplasmic domains required for the interaction of polycystin-2 with polycystin-1 [ PUBMED:9326320 ]. PKD2, although clinically milder than PKD1, has a deleterious impact on life expectancy.

This entry contains proteins belonging to the polycystin family including Mucolipin and Polycystin-1 and -2 (PKD1 and PKD2). The domain contains the cation channel region of PKD1 and PKD2 proteins. PKD1 and PKD2 may function through a common signalling pathway that is necessary for normal tubulogenesis. The PKD2 gene product has six transmembrane spans with intracellular amino- and carboxyl-termini [ PUBMED:8650545 ].

Mucolipin is a cationic channel which probably plays a role in the endocytic pathway and in the control of membrane trafficking of proteins and lipids. It could play a major role in the calcium ion transport regulating lysosomal exocytosis [ PUBMED:11013137 , PUBMED:12459486 , PUBMED:14749347 ].

Domain organisation

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

Loading domain graphics...

Pfam Clan

This family is a member of clan Ion_channel (CL0030), which has the following description:

This superfamily contains a diverse range of ion channels that share a pair of transmembrane helices in common. This clan is classified as the VIC (Voltage-gated Ion Channel) superfamily in TCDB.

The clan contains the following 7 members:

Ion_trans Ion_trans_2 IRK KdpA Lig_chan PKD_channel TrkH


We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets and the UniProtKB sequence database. More...

View options

We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

Representative proteomes UniProt
Jalview View  View  View  View  View  View  View 
HTML View             
PP/heatmap 1            

1Cannot generate PP/Heatmap alignments for seeds; no PP data available

Key: ✓ available, x not generated, not available.

Format an alignment

Representative proteomes UniProt

Download options

We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.

Representative proteomes UniProt
Raw Stockholm Download   Download   Download   Download   Download   Download   Download  
Gzipped Download   Download   Download   Download   Download   Download   Download  

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

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...


This page displays the phylogenetic tree for this family's seed alignment. 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 alignment.

Note: You can also download the data file for the tree.

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 View help on the curation process

Seed source: Bateman A
Previous IDs: none
Type: Family
Sequence Ontology: SO:0100021
Author: Bateman A
Number in seed: 11
Number in full: 5251
Average length of the domain: 267.80 aa
Average identity of full alignment: 21 %
Average coverage of the sequence by the domain: 25.08 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 19.9 19.9
Trusted cut-off 19.9 19.9
Noise cut-off 19.8 19.8
Model length: 426
Family (HMM) version: 14
Download: download the raw HMM for this family

Species distribution

Sunburst controls


Weight segments by...

Change the size of the sunburst


Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


Align selected sequences to HMM

Generate a FASTA-format file

Clear selection

This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...

Loading sunburst data...

Tree controls


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


Please note: for large trees this can take some time. While the tree is loading, you can safely switch away from this tab but if you browse away from the family page entirely, the tree will not be loaded.


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 PKD_channel domain has been found. There are 108 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 sequence.

Loading structure mapping...