Summary: Eukaryotic porin

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

Wikipedia: Voltage-dependent anion channel
Pfam
InterPro

This is the Wikipedia entry entitled "Voltage-dependent anion channel". More...

The Wikipedia text that you see displayed here is a download from Wikipedia. This means that the information we display is a copy of the information from the Wikipedia database. The button next to the article title ("Edit Wikipedia article") takes you to the edit page for the article directly within Wikipedia. You should be aware you are not editing our local copy of this information. Any changes that you make to the Wikipedia article will not be displayed here until we next download the article from Wikipedia. We currently download new content on a nightly basis.

Does Pfam agree with the content of the Wikipedia entry ?

Pfam has chosen to link families to Wikipedia articles. In some case we have created or edited these articles but in many other cases we have not made any direct contribution to the content of the article. The Wikipedia community does monitor edits to try to ensure that (a) the quality of article annotation increases, and (b) vandalism is very quickly dealt with. However, we would like to emphasise that Pfam does not curate the Wikipedia entries and we cannot guarantee the accuracy of the information on the Wikipedia page.

Editing Wikipedia articles

Before you edit for the first time

Wikipedia is a free, online encyclopedia. Although anyone can edit or contribute to an article, Wikipedia has some strong editing guidelines and policies, which promote the Wikipedia standard of style and etiquette. Your edits and contributions are more likely to be accepted (and remain) if they are in accordance with this policy.

You should take a few minutes to view the following pages:

How your contribution will be recorded

Anyone can edit a Wikipedia entry. You can do this either as a new user or you can register with Wikipedia and log on. When you click on the "Edit Wikipedia article" button, your browser will direct you to the edit page for this entry in Wikipedia. If you are a registered user and currently logged in, your changes will be recorded under your Wikipedia user name. However, if you are not a registered user or are not logged on, your changes will be logged under your computer's IP address. This has two main implications. Firstly, as a registered Wikipedia user your edits are more likely seen as valuable contribution (although all edits are open to community scrutiny regardless). Secondly, if you edit under an IP address you may be sharing this IP address with other users. If your IP address has previously been blocked (due to being flagged as a source of 'vandalism') your edits will also be blocked. You can find more information on this and creating a user account at Wikipedia.

If you have problems editing a particular page, contact us at pfam-help@sanger.ac.uk and we will try to help.

Contact us

The community annotation is a new facility of the Pfam web site. If you have problems editing or experience problems with these pages please contact us.

Voltage-dependent anion channel Edit Wikipedia article

Crystal Structure of the Human Voltage-Dependent Anion Channel. The arrows denote the antiparallel beta sheets that form the characteristic beta-barrel

Eukaryotic porin

Identifiers

Symbol

Porin_3

Available protein structures:
Pfam	structures
PDB	RCSB PDB; PDBe
PDBsum	structure summary

Voltage-dependent anion channels are a class of porin ion channel located on the outer mitochondrial membrane.^[1] There is debate as to whether or not this channel is expressed in the cell surface membrane.^[2] ^[3]^[4]

This major protein of the outer mitochondrial membrane of eukaryotes forms a voltage-dependent anion-selective channel (VDAC) that behaves as a general diffusion pore for small hydrophilic molecules.^[5]^[6]^[7]^[8] The channel adopts an open conformation at low or zero membrane potential and a closed conformation at potentials above 30-40 mV. VDAC facilitates the exchange of ions and molecules between mitochondria and cytosol and is regulated by the interactions with other proteins and small molecules.^[9]

[edit] Structure

This protein contains about 280 amino acids and forms a beta barrel which spans span the mitochondrial outer membrane.^[10]^[11]

Since its discovery in 1976, extensive function and structure analysis of VDAC proteins has been conducted. A prominent feature of the pore emerged: when reconstituted into planar lipid bilayers, there is a voltage-dependent switch between an anion-selective high-conductance state with high metabolite flux and a cation-selective low-conductance state with limited passage of metabolites.

More than 30 years after its initial discovery, in 2008, three independent structural projects of VDAC-1 were completed. The first was solved by multi-dimensional NMR spectroscopy. The second applied a hybrid approach using crystallographic data. The third was for mouse VDAC-1 crystals determined by X-ray crystallographic techniques. The three projects of the 3D structures of VDAC-1 revealed many structural features. First, VDAC-1 represents a new structural class of outer membrane β-barrel proteins with an odd number of strands. Another aspect is that the negatively charged side chain of residue E73 is oriented towards the hydrophobic membrane environment. The 19-stranded 3D structure obtained under different experimental sources by three different laboratories fits the EM and AFM data from native membrane sources and represents a biologically relevant state of VDAC-1.^[9]

[edit] Mechanism

At membrane potentials exceeding 30 mV (positive or negative), VDAC assumes a closed state, and transitions to its open state once the voltage drops below this threshold. Although both states allow passage of simple salts, VDAC is much more stringent with organic anions, a category into which most metabolites fall. ^[12] The precise mechanism for coupling voltage changes to conformational changes within the protein has not yet been worked out, but studies by Thomas et al. suggest that when the protein transitions to the closed form, voltage changes lead to the removal of a large section of the protein from the channel and decrease effective pore radius. ^[13] Several lysine residues, as well as Glu-152, have been implicated as especially important sensor residues within the protein. ^[14]

[edit] Biological Function

The voltage-dependent ion channel plays a key role in regulating metabolic and energetic flux across the outer mitochondrial membrane. It is involved in the transport of ATP, ADP, pyruvate, malate, and other metabolites, and thus communicates extensively with enzymes from metabolic pathways. ^[12] The ATP-dependent cytosolic enzymes hexokinase, glucokinase, and glycerol kinase, as well as the mitochondrial enzyme creatine kinase, have all been found to bind to VDAC. This binding puts them in close proximity to ATP released from the mitchondria. In particular, the binding of hexokinase is presumed to play a key role in coupling glycolysis to oxidative phosphorylation. ^[13] Additionally, VDAC is an important regulator of Ca²⁺ transport in and out of the mitochondria. Because Ca²⁺ is a cofactor for metabolic enzymes such as pyruvate dehydrogenase and isocitrate dehydrogenase, energetic production and homeostasis are both affected by VDAC’s permeability to Ca²⁺. ^[15]

[edit] Disease Relevance

VDAC has also been shown to play a role in apoptosis. ^[16] During apoptosis, increased permeability of VDAC allows for the release of apoptogenic factors such as cytochrome c. Although cyt. c plays an essential role in oxidative phosphorylation within the mitochondrion, in the cytosol it activates proteolytic enzymes called caspases, which play a major role in cell death.^[17] Although the mechanism for VDAC-facilitated cyt. c release has not yet been fully elucidated, some research suggests that oligomerization between individual subunits may create a large flexible pore through which cyt. c can pass.^[18]A more important factor is that release of cyt c. is also regulated by the Bcl-2 protein family: Bax interacts directly with VDAC to increase pore size and promote cyt. c release, while anti-apoptotic Bcl-xL produces the exact opposite effect.^[19] In fact, it has been shown that antibodies that inhibit VDAC also interfer with Bax-mediated cyt. c release in both isolated mitchondria and whole cells.^[20] This key role in apoptosis suggests VDAC as a potential target for chemotherapeutic drugs.

[edit] Examples

Yeast contains two members of this family (genes POR1 and POR2); vertebrates have at least three members (genes VDAC1, VDAC2 and VDAC3).^[10]

Humans like most higher eukaryotes encode three different VDACs; VDAC1, VDAC2, and VDAC3. Together with TOMM40 and TOMM40L they represent a family of evolutionarily related β-barrels.^[21]

[edit] References

^ Hoogenboom BW, Suda K, Engel A, Fotiadis D (2007). "The supramolecular assemblies of voltage-dependent anion channels in the native membrane". J. Mol. Biol. 370 (2): 246–55. doi:10.1016/j.jmb.2007.04.073. PMID 17524423.
^ Sabirov, R. Z.; Merzlyak, P. G. (2012). "Plasmalemmal VDAC controversies and maxi-anion channel puzzle". Biochimica et Biophysica Acta (BBA) - Biomembranes 1818 (6): 1570. doi:10.1016/j.bbamem.2011.09.024. edit
^ De Pinto, V.; Messina, A.; Lane, D. J. R.; Lawen, A. (2010). "Voltage-dependent anion-selective channel (VDAC) in the plasma membrane". FEBS Letters 584 (9): 1793–1799. doi:10.1016/j.febslet.2010.02.049. PMID 20184885. edit
^ Niehage, C.; Steenblock, C.; Pursche, T.; Bornhäuser, M.; Corbeil, D.; Hoflack, B. (2011). "The Cell Surface Proteome of Human Mesenchymal Stromal Cells". In Borlongan, Cesario V. PLoS ONE 6 (5): e20399. doi:10.1371/journal.pone.0020399. PMC 3102717. PMID 21637820. edit
^ Benz R (1994). "Permeation of hydrophilic solutes through mitochondrial outer membranes: review on mitochondrial porins". Biochim. Biophys. Acta 1197 (2): 167–196. doi:10.1016/0304-4157(94)90004-3. PMID 8031826.
^ Mannella CA (1992). "The 'ins' and 'outs' of mitochondrial membrane channels". Trends Biochem. Sci. 17 (8): 315–320. doi:10.1016/0968-0004(92)90444-E. PMID 1384178.
^ Dihanich M (1990). "The biogenesis and function of eukaryotic porins". Experientia 46 (2): 146–153. doi:10.1007/BF02027310. PMID 1689252.
^ Forte M, Guy HR, Mannella CA (1987). "Molecular genetics of the VDAC ion channel: structural model and sequence analysis". J. Bioenerg. Biomembr. 19 (4): 341–350. doi:10.1007/BF00768537. PMID 2442148.
^ ^a ^b Hiller S, Abramson J, Mannella C, Wagner G, Zeth K (September 2010). "The 3D structures of VDAC represent a native conformation". Trends Biochem. Sci. 35 (9): 514–21. doi:10.1016/j.tibs.2010.03.005. PMC 2933295. PMID 20708406.
^ ^a ^b Sampson MJ, Lovell RS, Davison DB, Craigen WJ (1996). "A novel mouse mitochondrial voltage-dependent anion channel gene localizes to chromosome 8". Genomics 36 (1): 192–196. doi:10.1006/geno.1996.0445. PMID 8812436.
^ Zeth K (2010). "Structure and evolution of mitochondrial outer membrane proteins of beta-barrel topology". Biochim. Biophys. Acta 1797 (6–7): 1292–9. doi:10.1016/j.bbabio.2010.04.019. PMID 20450883.
^ ^a ^b Blachly-Dyson, E. and Forte, M. (2001). "VDAC Channels". IUBMB Life 52 (3-5): 113–18. doi:10.1080/15216540152845902. PMID 11798022.
^ ^a ^b Colombini, M., Blachly-Dyson, E., Forte, M. (1996). "VDAC, a channel in the outher mitochondrial membrane". Ion Channels 4: 162–209. PMID 8744209.
^ Colombini, M., Blachly-Dyson, E., Forte, M. (1993). "Mapping of residues forming the voltage sensor of the voltage-dependent anion-selective channel". Proc. Natl. Acad. Sci. USA 90 (12): 5446–49. PMID 7685903. Unknown parameter |pmcid= ignored (help)
^ Shoshan-Barmatz V, Gincel D. (2003). "The voltage-dependent anion channel: characterization, modulation, and role in mitochondrial function in cell life and death.". Cell Biochem. Biophys. 39 (3): 279–92. doi:10.1385/CBB:39:3:279. PMID 14716081.
^ Lemasters JJ, Holmuhamedov E. (2006). "Voltage-dependent anion channel (VDAC) as mitochondrial governator--thinking outside the box.". Biochim. Biophys. Acta. 1762 (2): 181–90. doi:10.1016/j.bbadis.2005.10.006. PMID 16307870.
^ Tsujimoto Y, Shimizu S. (2002). "The voltage-dependent anion channel: an essential player in apoptosis.". Biochimie 84 (2-3): 187–93. doi:10.1016/S0300-9084(02)01370-6. PMID 12022949.
^ Zalk R, Israelson A, Garty ES, Azoulay-Zohar H, Shoshan-Barmatz V. (2005). "Oligomeric states of the voltage-dependent anion channel and cytochrome c release from mitochondria". Biochem J. 386 (1): 73–83. doi:10.1042/BJ20041356. PMID 15456403.
^ Shimizu S, Narita M, Tsujimoto Y. (1999). "Bcl-2 family proteins regulate the release of apoptogenic cytochrome c by the mitochondrial channel VDAC". Nature 399 (6735): 483–7. doi:10.1038/20959. PMID 10365962.
^ Shimizu S, Matsuoka Y, Shinohara Y, Yoneda Y, Tsujimoto Y. (2001). "Essential role of voltage-dependent anion channel in various forms of apoptosis in mammalian cells.". J. Cell Biol. 152 (2): 237–50. doi:10.1083/jcb.152.2.237. PMID 11266442.
^ Bay DC, Hafez M, Young MJ, Court DA (June 2012). "Phylogenetic and coevolutionary analysis of the β-barrel protein family comprised of mitochondrial porin (VDAC) and Tom40". Biochim. Biophys. Acta 1818 (6): 1502–19. doi:10.1016/j.bbamem.2011.11.027. PMID 22178864.

[edit] External links

Voltage-Dependent Anion Channels at the US National Library of Medicine Medical Subject Headings (MeSH)

This membrane protein-related article is a stub. You can help Wikipedia by expanding it.

Membrane transport protein: ion channels (TC 1A)

Ca²⁺: Calcium channel

Ligand-gated	Inositol trisphosphate receptor (1, 2, 3) · Ryanodine receptor (1, 2, 3)

Voltage-gated	L-type/Ca_vα (1.1, 1.2, 1.3, 1.4) · N-type/Ca_vα2.2 · P-type/Ca_vα(2.1) · Q-type/Ca_vα2.1 · R-type/Ca_vα2.3 · T-type/Ca_vα(3.1, 3.2, 3.3) α₂δ-subunits (1, 2) · β-subunits (β1, β2, β3, β4) · γ-subunits (γ1, γ2, γ3, γ4) Cation channels of sperm (1, 2, 3, 4) · Two-pore channel (1, 2)

Na⁺: Sodium channel

Constitutively active	Epithelial sodium channel (α, β, γ, δ)

Proton-gated	Amiloride-sensitive cation channel (1, 2, 3, 4)

Voltage-gated	Na_vα (1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 7A) · Na_vβ (1, 2, 3, 4)

K⁺: Potassium channel

Calcium-activated	BK channel (α1, β1, β2, β3, β4) · SK channel (SK1, SK2, SK3) · IK channel (IK1) · K_Ca (1.1, 2.1, 2.2, 2.3, 3.1, 4.1, 4.2, 5.1)

Inward-rectifier	K_ATP · K_ir (1.1, 2.1, 2.2, 2.3, 2.4, 2.6) · GIRK/K_ir (3.1, 3.2, 3.3, 3.4) · K_ir (4.1, 4.2, 5.1, 6.1, 6.2, 7.1)

Tandem pore domain	K2P (1, 2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 15, 16, 17, 18)

Voltage-gated	K_vα1-6 (1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8) · (2.1, 2.2) · (3.1, 3.2, 3.3, 3.4) · (4.1, 4.2, 4.3) · (5.1) · (6.1, 6.2, 6.3, 6.4) K_vα7-12 (7.1, 7.2, 7.3, 7.4, 7.5) · (8.1, 8.2) · (9.1, 9.2, 9.3) · (10.1, 10.2) · (11.1/hERG, 11.2, 11.3) · (12.1, 12.2, 12.3) K_vβ (1, 2, 3) · KCNIP (1, 2, 3, 4) · minK/ISK · minK/ISK-like · MiRP (1, 2, 3) · Shaker gene

Miscellaneous

Cl^-: Chloride channel	ANO1 · Bestrophin (1, 2) · CFTR · CLCA (1, 2, 3, 4) · CLCN (1, 2, 3, 4, 5, 6, 7, KA, KB) · CLIC (1, 2, 3, 4, 5, 6, L1) · CLNS (1A, 1B)

H⁺: Proton channel	HVCN1

M⁺: CNG cation channel	α (1, 2, 3, 4) · β (1, 2, 3) · HCN (FC, 1, 2, 3, 4)

M⁺: TRP cation channel	TRPA (1) · TRPC (1, 2, 3, 4, 4AP, 5, 6, 7) · TRPM (1, 2, 3, 4, 5, 6, 7, 8) · TRPML (1, 2, 3) · TRPN · TRPP (1, 2) · TRPV (1, 2, 3, 4, 5, 6)

H₂O (+ solutes): Porin	Aquaporin (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) · Voltage-dependent anion channel (1, 2, 3) · General bacterial porin family

Cytoplasm: Gap junction	Connexin: A (GJA1, GJA3, GJA4, GJA5, GJA8, GJA9, GJA10) · B (GJB1, GJB2, GJB3, GJB4, GJB5, GJB6, GJB7) · C (GJC1, GJC2, GJC3) · D (GJD2, GJD3, GJD4)) Innexin

By gating mechanism

Ion channel class	Ligand-gated · Light-gated · Voltage-gated · Stretch-activated

see also disorders
B memb: cead, trns (1A, 1C, 1F, 2A, 3A1, 3A2-3, 3D), othr

This article incorporates text from the public domain Pfam and InterPro IPR001925

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

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.

Eukaryotic porin Provide feedback

No Pfam abstract.

External database links

PANDIT:	PF01459
PROSITE:	PDOC00483
Pseudofam:	PF01459
SYSTERS:	Porin_3
Transporter classification:	1.B.8 3.A.8

This tab holds annotation information from the InterPro database.

InterPro entry IPR001925

The major protein of the outer mitochondrial membrane of eukaryotes is a porin that forms a voltage-dependent anion-selective channel (VDAC) that behaves as a general diffusion pore for small hydrophilic molecules [PUBMED:8031826, PUBMED:1384178, PUBMED:1689252, PUBMED:2442148]. The channel adopts an open conformation at low or zero membrane potential and a closed conformation at potentials above 30-40 mV.

This protein contains about 280 amino acids and its sequence is composed of between 12 to 16 beta-strands that span the mitochondrial outer membrane. Yeast contains two members of this family (genes POR1 and POR2); vertebrates have at least three members (genes VDAC1, VDAC2 and VDAC3) [PUBMED:8812436].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Cellular component	mitochondrial outer membrane (GO:0005741)
Molecular function	voltage-gated anion channel activity (GO:0008308)
Biological process	anion transport (GO:0006820)
	transmembrane transport (GO:0055085)
	regulation of anion transport (GO:0044070)

Domain organisation

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

Loading domain graphics...

Alignments

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 using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the NCBI sequence database, and our metagenomics sequence database. More...

There are various ways to view or download the sequence alignments that we store. We provide several sequence viewers and a plain-text Stockholm-format file for download.

Alignment types

We make a range of alignments for each Pfam-A family:

seed: the curated alignment from which the HMM for the family is built
full: the alignment generated by searching the sequence database using the HMM
RP15/RP35/RP55/RP75: Representative Proteomes (RPs) at 15%, 35%, 55% and 75% co-membership thresholds
NCBI: alignment generated by searching the NCBI sequence database using the family HMM
meta: alignment generated by searching the metagenomics sequence database using the family HMM

Viewing

You can see the alignments as HTML or in three different sequence viewers:

jalview: a Java applet developed at the University of Dundee. You will need Java installed before running jalview
HTML: an HTML page showing the whole alignment.Please note: full Pfam alignments can be very large. These HTML views are extremely large and often cause problems for browsers. Please use either jalview or the Pfam viewer if you have trouble viewing the HTML version
PP/Heatmap: an HTML-based representation of the alignment, coloured according to the posterior-probability (PP) values from the HMM. As for the standard HTML view, heatmap alignments can also be very large and slow to render.
Pfam viewer: an HTML-based viewer that uses DAS to retrieve alignment fragments on request

Reformatting

You can download (or view in your browser) a text representation of a Pfam alignment in various formats:

Selex
Stockholm
FASTA
MSF

You can also change the order in which sequences are listed in the alignment, change how insertions are represented, alter the characters that are used to represent gaps in sequences and, finally, choose whether to download the alignment or to view it in your browser directly.

Downloading

You may find that large alignments cause problems for the viewers and the reformatting tool, so we also provide all alignments in Stockholm format. You can download either the plain text alignment, or a gzipped version of it.

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.

	Seed (90)	Full (1317)	Representative proteomes				NCBI (1211)	Meta (9)
	Seed (90)	Full (1317)	RP15 (215)	RP35 (374)	RP55 (573)	RP75 (757)	NCBI (1211)	Meta (9)
Jalview	View	View	View	View	View	View	View	View
HTML	View	View	View	View	View	View
PP/heatmap	₁	View	View	View	View	View
Pfam viewer	View	View

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

Key: available, not generated, — not available.

Format an alignment

	Seed (90)	Full (1317)	Representative proteomes				NCBI (1211)	Meta (9)
	Seed (90)	Full (1317)	RP15 (215)	RP35 (374)	RP55 (573)	RP75 (757)	NCBI (1211)	Meta (9)
Alignment:
Format:
Order:	Tree Alphabetical
Sequence:	Inserts lower case All upper case
Gaps:
Download/view:	Download View

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.

	Seed (90)	Full (1317)	Representative proteomes				NCBI (1211)	Meta (9)
	Seed (90)	Full (1317)	RP15 (215)	RP35 (374)	RP55 (573)	RP75 (757)	NCBI (1211)	Meta (9)
Raw Stockholm	Download	Download	Download	Download	Download	Download	Download	Download
Gzipped	Download	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.

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'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

Seed source:

Prodom_3211 (release 99.1) & Pfam-B__3211 (release 7.5)

Previous IDs:

Euk_porin;

Type:

Family

Author:

Bateman A

Number in seed:

90

Number in full:

1317

Average length of the domain:

250.60 aa

Average identity of full alignment:

22 %

Average coverage of the sequence by the domain:

88.76 %

HMM information

HMM build commands:

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

search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq

Model details:

Parameter	Sequence	Domain
Gathering cut-off	26.9	26.9
Trusted cut-off	26.9	27.3
Noise cut-off	26.5	26.8

Model length:

273

Family (HMM) version:

17

Download:

download the raw HMM for this family

Species distribution

Sunburst
Tree

Sunburst controls

Show

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...

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, its 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.

Loading sunburst data...

Tree controls

Hide

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
save a plain text representation of the tree

Loading...

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.

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 Porin_3 domain has been found. There are 3 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.

Loading structure mapping...

Archea	Eukaryota
Bacteria	Other sequences
Viruses	Unclassified
Viroids	Unclassified sequence

Family: Porin_3 (PF01459)

Jump to...