Summary: Polycystin cation channel

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Polycystin cation channel

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

Literature references

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
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

Clan

This family is a member of clan Ion_channel (CL0030), which has a total of 7 members.

Internal database links

Similarity to PfamA using HHSearch:

Ion_trans

External database links

PANDIT:	PF08016
Pseudofam:	PF08016
SYSTERS:	PKD_channel

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...

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Pfam Clan

This family is a member of clan Ion_channel (CL0030), which contains the following 7 members:

Ion_trans Ion_trans_2 IRK KdpA Lig_chan PKD_channel TrkH

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 (13) Full (686) NCBI (3691) Metagenomics (434)
Viewer:

Formatting options

Alignment:	Seed (13) Full (686)
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 (13) Full (686) NCBI (3691) Metagenomics (434)
Full length sequences	Full-sequences (686)

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 HMMER3.

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:

Bateman A

Previous IDs:

none

Type:

Family

Author:

Bateman A

Number in seed:

13

Number in full:

686

Average length of the domain:

269.90 aa

Average identity of full alignment:

18 %

Average coverage of the sequence by the domain:

23.99 %

HMM information

HMM build commands:

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

search method: hmmsearch -Z 15929002 -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:

7

Download:

download the raw HMM for this family

Species distribution

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Colour assignments

Archea	Eukaryota
Bacteria	Other sequences
Viruses	Unclassified
Viroids	Unclassified sequence

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 if you need to select sub-trees and view sequence alignments. More...

This chart is a modified "sunburst" visualisation of the species tree for this family. It shows each node in the tree as a separate arc, arranged radially with the superkingdoms at the centre and the species arrayed around the outermost ring.

How the sunburst is generated

The tree is built by considering the taxonomic lineage of each sequence that has a match to this family. For each node in the resulting tree, we draw an arc in the sunburst. The radius of the arc, it's distance from the root node at the centre of the sunburst, shows the taxonomic level ("superkingdom", "kingdom", etc). The length of the arc represents either the number of sequences represented at a given level, or the number of species that are found beneath the node in the tree. The weighting scheme can be changed using the sunburst controls.

In order to reduce the complexity of the representation, we reduce the number of taxonomic levels that we show. We consider only the following eight major taxonomic levels:

superkingdom
kingdom
phylum
class
order
family
genus
species

Colouring and labels

Segments of the tree are coloured approximately according to their superkingdom. For example, archeal branches are coloured with shades of orange, eukaryotes in shades of purple, etc. The colour assignments are shown under the sunburst controls. Where space allows, the name of the taxonomic level will be written on the arc itself.

As you move your mouse across the sunburst, the current node will be highlighted. In the top section of the controls panel we show a summary of the lineage of the currently highlighed node. If you pause over an arc, a tooltip will be shown, giving the name of the taxonomic level in the title and a summary of the number of sequences and species below that node in the tree.

Anomalies in the taxonomy tree

There are some situations that the sunburst tree cannot easily handle and for which we have work-arounds in place.

Missing taxonomic levels

Some species in the taxonomic tree may not have one or more of the main eight levels that we display. For example, Bos taurus is not assigned an order in the NCBI taxonomic tree. In such cases we mark the omitted level with, for example, "No order", in both the tooltip and the lineage summary.

Unmapped species names

The tree is built by looking at each sequence in the full alignment for the family. We take the name of the species given by UniProt and try to map that to the full taxonomic tree from NCBI. In some cases, the name chosen by UniProt does not map to any node in the NCBI tree, perhaps because the chosen name is listed as a synonym or a misspelling in the NCBI taxonomy.

So that these nodes are not simply omitted from the sunburst tree, we group them together in a separate branch (or segment of the sunburst tree). Since we cannot determine the lineage for these unmapped species, we show all levels between the superkingdom and the species as "uncategorised".

Sub-species

Since we reduce the species tree to only the eight main taxonomic levels, sequences that are mapped to the sub-species level in the tree would not normally be shown. Rather than leave out these species, we map them instead to their parent species. So, for example, for sequences belonging to one of the Vibrio cholerae sub-species in the NCBI taxonomy, we show them instead as belonging to the species Vibrio cholerae.

Too many species/sequences

For large species trees, you may see blank regions in the outer layers of the sunburst. These occur when there are large numbers of arcs to be drawn in a small space. If an arc is less than approximately one pixel wide, it will not be drawn and the space will be left blank. You may still be able to get some information about the species in that region by moving your mouse across the area, but since each arc will be very small, it will be difficult to accurately locate a particular species.

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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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Family: PKD_channel (PF08016)

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