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Innexin Edit Wikipedia article
An innexin is a member of a family of proteins that create gap junctions in invertebrates. The innexin proteins have four transmembrane spanning units and, like the vertebrate connexin gap junction protein, six innexin subunits together form a channel, an "innexon", in the plasma membrane between the inside and outside of the cell. Two innexons in apposed plasma membranes can form a gap junction. Innexin genes have homologues in vertebrates called pannexins. However, increasing evidence suggests that pannexons do not form gap junctions unless overexpressed in tissue. Thus, pannexins and innexins differ functionality and should be treated as separate families.
These proteins have been named innexins. Gap junctions are composed of membrane proteins that form a channel permeable to ions and small molecules connecting the cytoplasm of adjacent cells. Although gap junctions provide similar functions in all multicellular organisms, until the late 1990s it was not known what proteins invertebrates used for this purpose. While the connexin family of gap junction proteins was well-characterised in vertebrates, no homologs were found in non-chordates. Gap junction molecules with no sequence homology to connexins were initially identified in fruit flies. It was suggested that these proteins are specific invertebrate gap junctions, and they were thus named "innexins" (invertebrate analog of connexins). They were later identified in diverse invertebrates. Once the human genome was sequenced, innexin homologs were identified in humans and then in other vertebrates, indicating their ubiquitous distribution in the animal kingdom. They were called "pannexins" (from the Greek pan - all, throughout, and Latin nexus - connection, bond).
Genomes of vertebrates carry probably a conserved set of three pannexin paralogs (PANX1, PANX2 and PANX3). Invertebrate genomes may contain more than a dozen pannexin (innexin) genes. Vinnexins, viral homologs of pannexins/innexins, were identified in Polydnaviruses that occur in obligate symbiotic associations with parasitoid wasps. It was suggested that virally encoded vinnexin proteins may function to alter gap junction proteins in infected host cells, possibly modifying cell-cell communication during encapsulation responses in parasitized insects. Structurally pannexins are similar to connexins. Both types of protein consist of a cytoplasmic N-terminal domain, followed by four transmembrane segments that delimit two extracellular and one cytoplasmic loops; the C- terminal domain is cytoplasmic.
- C. elegans
- Hirudo medicinalis
- Bao, L.; Samuels, S.; Locovei, S.; MacAgno, E.; Muller, K.; Dahl, G. (2007). "Innexins Form Two Types of Channels". FEBS Letters 581 (29): 5703–5708. doi:10.1016/j.febslet.2007.11.030. PMC 2489203. PMID 18035059.
- Dahl G. & Harris A. 2009. Pannexins or Connexins? Chapter 12. In: A. Harris, D. Locke (eds.), Connexins: A Guide DOI 10.1007/978-1-59745-489-6_12,
- Lee R, Phelan P, Stebbings LA, Baines RA, Bacon JP, Davies JA, Ford C, Todman MG, Avery L, Barnes TM, Hekimi S, Shaw JE, Starich TA, Curtin KD, Wyman RJ, Sun YA (1998). "Innexins: a family of invertebrate gap-junction proteins". Trends Genet. 14 (9): 348–349. doi:10.1016/S0168-9525(98)01547-9. PMID 9769729.
- Phelan P, Stebbings LA, Baines RA, Bacon JP, Davies JA, Ford C (1998). "Drosophila Shaking-B protein forms gap junctions in paired Xenopus oocytes". Nature 391 (6663): 181–184. doi:10.1038/34426. PMID 9428764.
- Lukyanov S, Usman N, Panchin Y, Kelmanson I, Matz M, Lukyanov K (2000). "A ubiquitous family of putative gap junction molecules". Curr. Biol. 10 (13): –. doi:10.1016/S0960-9822(00)00576-5. PMID 10898987.
- Matz MV, Lukyanov SA, Kelmanson IV, Shagin DA, Usman N, Panchin YV (2002). "Altering electrical connections in the nervous system of the pteropod mollusc Clione limacina by neuronal injections of gap junction mRNA". Eur. J. Neurosci. 16 (12): 2475–2476. doi:10.1046/j.1460-9568.2002.02423.x. PMID 12492443.
- Turnbull M, Webb B (2002). "Perspectives on polydnavirus origins and evolution". Adv. Virus Res. 58: 203–254. doi:10.1016/S0065-3527(02)58006-4. PMID 12205780.
- Kroemer JA, Webb BA (2004). "Polydnavirus genes and genomes: emerging gene families and new insights into polydnavirus replication". Annu Rev Entomol 49 (1): 431–456. doi:10.1146/annurev.ento.49.072103.120132. PMID 14651471.
- Phelan P, Bacon J, Davies J, Stebbings L, Todman M, Avery L, Baines R, Barnes T, Ford C, Hekimi S, Lee R, Shaw J, Starich T, Curtin K, Sun Y, Wyman R (1998). "Innexins: a family of invertebrate gap-junction proteins.". Trends Genet 14 (9): 348–9. doi:10.1016/S0168-9525(98)01547-9. PMID 9769729.
- Phelan P, Stebbings L, Baines R, Bacon J, Davies J, Ford C (1998). "Drosophila Shaking-B protein forms gap junctions in paired Xenopus oocytes.". Nature 391 (6663): 181–4. doi:10.1038/34426. PMID 9428764.
- Dykes I, Macagno E (2006). "Molecular characterization and embryonic expression of innexins in the leech Hirudo medicinalis.". Dev Genes Evol 216 (4): 185–97. doi:10.1007/s00427-005-0048-1. PMID 16440200.
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Innexin Provide feedback
This family includes the drosophila proteins Ogre and shaking-B, and the C. elegans proteins Unc-7 and Unc-9. Members of this family are integral membrane proteins which are involved in the formation of gap junctions . This family has been named the Innexins .
Phelan P, Bacon JP, Davies JA, Stebbings LA, Todman MG, Avery L, Baines RA, Barnes TM, Ford C, Hekimi S, Lee R, Shaw JE, Starich TA, Curtin KD, Sun Y, Wyman RJ; , Trends Genet 1998;14:348-349.: Innexins: a family of invertebrate gap-junction proteins. PUBMED:9769729 EPMC:9769729
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR000990
The pannexin family combines invertebrate gap junction proteins and their vertebrate homologs. These proteins have been named innexins [PUBMED:9769729]. Gap junctions are composed of membrane proteins, which form a channel permeable for ions and small molecules connecting cytoplasm of adjacent cells. Although gap junctions provide similar functions in all multicellular organisms, until recently it was believed that vertebrates and invertebrates use unrelated proteins for this purpose. While the connexins family of gap junction proteins is well- characterised in vertebrates, no homologs have been found in invertebrates. In turn, gap junction molecules with no sequence homology to connexins have been identified in insects and nematodes. It has been suggested that these proteins are specific invertebrate gap junctions, and they were thus named innexins (invertebrate analog of connexins) [PUBMED:9428764]. As innexin homologs were recently identified in other taxonomic groups including vertebrates, indicating their ubiquitous distribution in the animal kingdom, they were called pannexins (from the Latin pan-all, throughout, and nexus-connection, bond) [PUBMED:10898987, PUBMED:12492443, PUBMED:5028292].
Genomes of vertebrates carry probably a conserved set of 3 pannexin paralogs (PANX1, PANX2 and PANX3). Invertebrate genomes may contain more than a dozen pannexin (innexin) genes. Vinnexins, viral homologs of pannexins/innexins, were identified in Polydnaviruses that occur in obligate symbiotic associations with parasitoid wasps. It was suggested that virally encoded vinnexin proteins may function to alter gap junction proteins in infected host cells, possibly modifying cell-cell communication during encapsulation responses in parasitized insects [PUBMED:12205780, PUBMED:14651471]. Structurally pannexins are simillar to connexins. Both types of protein consist of a cytoplasmic N-terminal domain, followed by four transmembrane segments that delimit two extracellular and one cytoplasmic loops; the C- terminal domain is cytoplasmic.
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Cellular component||gap junction (GO:0005921)|
Below is a listing of the unique domain organisations or architectures in which this domain is found. More...
The graphic that is shown by default represents the longest sequence with a given architecture. Each row contains the following information:
- the number of sequences which exhibit this architecture
a textual description of the architecture, e.g. Gla, EGF x 2, Trypsin.
This example describes an architecture with one
Gladomain, followed by two consecutive
EGFdomains, and finally a single
- a link to the page in the Pfam site showing information about the sequence that the graphic describes
- the UniProt description of the protein sequence
- the number of residues in the sequence
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Note that you can see the family page for a particular domain by clicking on the graphic. You can also choose to see all sequences which have a given architecture by clicking on the Show link in each row.
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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.
We make a range of alignments for each Pfam-A family:
- the curated alignment from which the HMM for the family is built
- the alignment generated by searching the sequence database using the HMM
- Representative Proteomes (RPs) at 15%, 35%, 55% and 75% co-membership thresholds
- alignment generated by searching the NCBI sequence database using the family HMM
- alignment generated by searching the metagenomics sequence database using the family HMM
You can see the alignments as HTML or in three different sequence viewers:
- a Java applet developed at the University of Dundee. You will need Java installed before running jalview
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- Pfam viewer
- an HTML-based viewer that uses DAS to retrieve alignment fragments on request
You can download (or view in your browser) a text representation of a Pfam alignment in various formats:
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.
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.
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.
1Cannot generate PP/Heatmap alignments for seeds; no PP data available
Key: available, not generated, — not available.
Format an alignment
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.
You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.
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 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...
If you find these logos useful in your own work, please consider citing the following article:
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.
|Seed source:||Pfam-B_779 (release 3.0)|
|Number in seed:||99|
|Number in full:||863|
|Average length of the domain:||283.30 aa|
|Average identity of full alignment:||22 %|
|Average coverage of the sequence by the domain:||76.49 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||13|
|Download:||download the raw HMM for this family|
Weight segments by...
Change the size of the sunburst
selected sequences to HMM
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- 0 sequences
- 0 species
This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the 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:
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".
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.
The tree shows the occurrence of this domain across different species. More...
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.
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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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.