Summary: PAS fold
Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.
This is the Wikipedia entry entitled "PAS domain". 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 email@example.com and we will try to help.
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.
PAS domain Edit Wikipedia article
A Per-Arnt-Sim (PAS) domain is a protein domain found in all kingdoms of life.  It is found in many signaling proteins, where it functions as a signaling sensor. Generally, the PAS domain acts as a molecular velcro, whereby small molecules and other proteins via association with the PAS domain. Due to this velcro capability, the PAS domain has been shown as the key structural motif involved in protein-protein interactions of the circadian clock.
PAS domains are found in a large number of organisms from bacteria to mammals. The PAS domain was named after the three proteins in which it was first discovered:
Per – period circadian protein
Sim – single-minded protein
Since the initial discovery the PAS domain, a a large quantity of PAS binding sites have been discovered in bacteria and eukaryotes, a subset of which are responsive to oxygen, light and voltage, which gives rise to PAS LOV proteins.
Although the PAS domain exhibits a degree of sequence variability, the three-dimensional structure of the PAS domain core is broadly conserved.  This core consists of a five-stranded antiparallel β-sheet and several α-helices. Structural changes, as a result of signaling, predominantly originate within the β-sheet. These signals propagate via the α-helices of the core to the covalently-attached effector domain.  In 1998, the PAS domain core architecture was first characterized in the the structure of Halorhodospira halophila photoactive yellow protein (PYP).  In many proteins, a dimer of PAS domains is required, whereby one binds a ligand, and the other mediates interactions with other proteins. 
Examples of PAS in Organisms
The PAS domains that are known share less than 20% average pairwise sequence identity, meaning they are surprisingly dissimilar.  PAS domains are frequently found on proteins with other environmental sensing mechanisms. An example of PAS B domain of Hif1a and Hif2a are oxygen-sensing domains.  Many PAS domains are attached to photoreceptive cells. 
Often in the bacterial kingdom, PAS domains are positioned at the amino terminus of signaling proteins such as sensor histidine kinases, cyclic-di-GMP synthases and hydrolases, and methyl-accepting chemotaxis proteins. 
|Genes in Drosophila||Binding Domains|
A PAS domain is found in the ZTL and NPH1 genes. These domains are very similar to the PAS domain found in the Neurospora circadian-associated protein WC-1. 
The circadian clock that currently understood for mammals begins when light activates BMAL1 and CLK to bind via their PAS domains. That activator complex regulates the Per1/Per2/Per3 which also has PAS, which it uses to bind to cryptochromes 1 and 2 (CRY 1,2 family), which do not contain PAS domains.
|Mammalian Genes||Binding Domains|
|Per1, 2, 3||PAS|
Other Mammalian PAS roles
Within Mammals both PAS domains play other important role. PAS A is responsible for the protein-protein interactions with other PAS proteins, while PAS B has a more versatile role. It mediates interactions with chaperonins and other small molecules like dioxin, but PAS B domains in NPAS2, a homolog of the Drosophila clk gene, and the Hypoxia Inducible Factor (HIF) also help to mediate ligand binding . Furthermore, PAS containing the NPAS2 protein have been shown to be a substitute for the Clock gene in mutant mice who lack the Clock gene completely. 
PAS also directly interacts with BHLH. It is typically located on the C-Terminus of the BHLH protein. PAS domains containing BHLH proteins form a BHLH-Pas protein, typically found and encoded in HIF and the Clock gene. 
- doi:10.1021/bi0343370. PMID 12820879.; Dunham CM, Dioum EM, Tuckerman JR, Gonzalez G, Scott WG, Gilles-Gonzalez MA (July 2003). "A distal arginine in oxygen-sensing heme-PAS domains is essential to ligand binding, signal transduction, and structure". Biochemistry. 42 (25): 7701–8.
- Henry, Jonathan T.; Crosson, Sean (1 January 2011). "Ligand-binding PAS domains in a genomic, cellular, and structural context". Annual Review of Microbiology. pp. 261–286. doi:10.1146/annurev-micro-121809-151631.
- Ponting CP, Aravind L (November 1997). "PAS: a multi-functional domain family comes to light". Curr. Biol. 7 (11): R674–7. doi:10.1016/S0960-9822(06)00352-6. PMID 9382818.
- Hefti MH, Françoijs KJ, de Vries SC, Dixon R, Vervoort J (March 2004). "The PAS fold. A redefinition of the PAS domain based upon structural prediction". Eur. J. Biochem. 271 (6): 1198–208. doi:10.1111/j.1432-1033.2004.04023.x. PMID 15009198.
- Liu, Yu C.; Machuca, Mayra A.; Beckham, Simone A.; Gunzburg, Menachem J.; Roujeinikova, Anna (1 October 2015). "Structural basis for amino-acid recognition and transmembrane signalling by tandem Per-Arnt-Sim (tandem PAS) chemoreceptor sensory domains". Acta Crystallographica. Section D, Biological Crystallography. pp. 2127–2136. doi:10.1107/S139900471501384X.
- Möglich, Andreas; Ayers, Rebecca A.; Moffat, Keith (14 October 2009). "Structure and signaling mechanism of Per-ARNT-Sim domains". Structure (London, England: 1993). pp. 1282–1294. doi:10.1016/j.str.2009.08.011.
- Hennig, Sven; Strauss, Holger M.; Vanselow, Katja; Yildiz, Özkan; Schulze, Sabrina; Arens, Julia; Kramer, Achim; Wolf, Eva (28 April 2009). "Structural and Functional Analyses of PAS Domain Interactions of the Clock Proteins Drosophila PERIOD and Mouse PERIOD2". PLOS Biology. pp. e1000094. doi:10.1371/journal.pbio.1000094.
- Nambu JR, Lewis JO, Wharton KA Jr, Crews ST (December 1990). "The Drosophila single-minded gene encodes a helix-loop-helix protein that acts as a master regulator of CNS midline development". Cell. 67 (6): 1157–67. doi:10.1016/0092-8674(91)90292-7. PMID 1760843.
- Rosato, Ezio; Tauber, Eran; Kyriacou, Charalambos P. (1 January 2006). "Molecular genetics of the fruit-fly circadian clock". European Journal of Human Genetics. pp. 729–738. doi:10.1038/sj.ejhg.5201547.
- Henry, Jonathan T.; Crosson, Sean (1 January 2011). "Ligand-Binding PAS Domains in a Genomic, Cellular, and Structural Context". Annual Review of Microbiology. pp. 261–286. doi:10.1146/annurev-micro-121809-151631.
- "Structure and Signaling Mechanism of Per-ARNT-Sim Domains" (PDF).
- McIntosh, Brian; Hogenesch, John; Bradfield, Christopher. "Mammalian Per-Arnt-Sim Proteins in Environmental Adaptation | Annual Review of Physiology". Annual Review of Physiology. doi:10.1146/annurev-physiol-021909-135922#_i21.
- Harmer, Stacey L.; Panda, Satchidananda; Kay, Steve A. (28 November 2003). "Molecular Bases of Circadian Rhythms". Annual Review of Cell and Developmental Biology. pp. 215–253. doi:10.1146/annurev.cellbio.17.1.215.
- Somers, David; Schultz, Thomas; Kay, Steve; Milnamow, Maureen. "ZEITLUPE Encodes a Novel Clock-Associated PAS Protein from Arabidopsis". ScienceDirect. Cell. doi:10.1016/S0092-8674(00)80841-7.
- Debruyne JP, Noton E, Lambert CM, Maywood ES, Weaver DR, Reppert SM (May 2006). "A clock shock: mouse CLOCK is not required for circadian oscillator function". Neuron. 50 (3): 465–77. doi:10.1016/j.neuron.2006.03.041. PMID 16675400.
- Jones, Susan (1 January 2004). "An overview of the basic helix-loop-helix proteins". Genome Biology. p. 226. doi:10.1186/gb-2004-5-6-226.
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.
PAS fold Provide feedback
The PAS fold corresponds to the structural domain that has previously been defined as PAS and PAC motifs . The PAS fold appears in archaea, eubacteria and eukarya.
Borgstahl GE, Williams DR, Getzoff ED; , Biochemistry 1995;34:6278-6287.: 1.4 A structure of photoactive yellow protein, a cytosolic photoreceptor: unusual fold, active site, and chromophore. PUBMED:7756254 EPMC:7756254
Hefti MH, Francoijs KJ, de Vries SC, Dixon R, Vervoort J; , Eur J Biochem 2004;271:1198-1208.: The PAS fold: a redefination of the PAS domain based upon structural prediction. PUBMED:15009198 EPMC:15009198
Internal database links
|SCOOP:||MEKHLA PAS PAS_10 PAS_11 PAS_4 PAS_7 PAS_8 PAS_9|
|Similarity to PfamA using HHSearch:||PAS PAS_4 PAS_9 PAS_11|
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR013655
The PAS fold corresponds to the structural domain that has previously been defined as PAS and PAC motifs [PUBMED:15009198]. The PAS fold appears in archaea, eubacteria and eukarya. The PAS domain contains a sensory box, or S-box domain that occupies the central portion of the PAS domain but is more widely distributed. It is often tandemly repeated. Known prosthetic groups bound in the S-box domain include haem in the oxygen sensor FixL [PUBMED:16681374], FAD in the redox potential sensor NifL [PUBMED:16417511], and a 4-hydroxycinnamyl chromophore in photoactive yellow protein [PUBMED:14979724]. Proteins containing the domain often contain other regulatory domains such as response regulator or sensor histidine kinase domains. Other S-box proteins include phytochromes and the aryl hydrocarbon receptor nuclear translocator.
This domain has been found in the gene product of the madA gene of the filamentous zygomycete fungus Phycomyces blakesleeanus. It has been shown that MadA encodes a blue-light photoreceptor for phototropism and other light responses. The gene is involved in the phototropic responses associated with sporangiophore growth; they exhibit phototropism by bending toward near-UV and blue wavelengths and away from far-UV wavelengths in a manner that is physiologically similar to plant phototropic responses [PUBMED:16537433].
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Molecular function||protein binding (GO:0005515)|
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
- the Pfam graphic itself.
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.
Finally, because some families can be found in a very large number of architectures, we load only the first fifty architectures by default. If you want to see more architectures, click the button at the bottom of the page to load the next set.
Loading domain graphics...
This clan contains PAS domains that are found in a wide variety of bacterial signaling proteins.
The clan contains the following 13 members:CpxA_peri MEKHLA PAS PAS_10 PAS_11 PAS_2 PAS_3 PAS_4 PAS_5 PAS_6 PAS_7 PAS_8 PAS_9
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, the UniProtKB sequence database, 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 UniProtKB sequence database using the family HMM
- 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
- 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
- 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.
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.
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_64 (Release 18.0)|
|Number in seed:||119|
|Number in full:||23723|
|Average length of the domain:||86.90 aa|
|Average identity of full alignment:||18 %|
|Average coverage of the sequence by the domain:||13.76 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 26740544 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||11|
|Download:||download the raw HMM for this family|
Weight segments by...
Change the size of the sunburst
selected sequences to HMM
a FASTA-format file
- 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
- save a plain text representation of the tree
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.
There is 1 interaction for this family. More...
We determine these interactions using iPfam, which considers the interactions between residues in three-dimensional protein structures and maps those interactions back to Pfam families. You can find more information about the iPfam algorithm in the journal article that accompanies the website.
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 PAS_3 domain has been found. There are 55 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...