Summary: Domain of unknown function (DUF2019)
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Domain of unknown function Edit Wikipedia article
A domain of unknown function (DUF) is a protein domain that has no characterised function. These families have been collected together in the Pfam database using the prefix DUF followed by a number, with examples being DUF2992 and DUF1220. As of 2019, there are almost 4,000 DUF families within the Pfam database representing over 22% of known families. Some DUFs are not named using the nomenclature due to popular usage but are nevertheless DUFs.
The DUF naming scheme was introduced by Chris Ponting, through the addition of DUF1 and DUF2 to the SMART database. These two domains were found to be widely distributed in bacterial signaling proteins. Subsequently, the functions of these domains were identified and they have since been renamed as the GGDEF domain and EAL domain respectively.
Structural genomics programmes have attempted to understand the function of DUFs through structure determination. The structures of over 250 DUF families have been solved. This (2009) work showed that about two thirds of DUF families had a structure similar to a previously solved one and therefore likely to be divergent members of existing protein superfamilies, whereas about one third possessed a novel protein fold.
Some DUF families share remote sequence homology with domains that has characterized function. Computational work can be used to link these relationships. An 2015 work was able to assign 20% of the DUFs to characterized structual superfamilies. Pfam also continuously perform the (manually-verified) assignment in "clan" superfamily entries.
Frequency and conservation
More than 20% of all protein domains were annotated as DUFs in 2013. About 2,700 DUFs are found in bacteria compared with just over 1,500 in eukaryotes. Over 800 DUFs are shared between bacteria and eukaryotes, and about 300 of these are also present in archaea. A total of 2,786 bacterial Pfam domains even occur in animals, including 320 DUFs.
Role in biology
Many DUFs are highly conserved, indicating an important role in biology. However, many such DUFs are not essential, hence their biological role often remains unknown. For instance, DUF143 is present in most bacteria and eukaryotic genomes. However, when it was deleted in Escherichia coli no obvious phenotype was detected. Later it was shown that the proteins that contain DUF143, are ribosomal silencing factors that block the assembly of the two ribosomal subunits. While this function is not essential, it helps the cells to adapt to low nutrient conditions by shutting down protein biosynthesis. As a result, these proteins and the DUF only become relevant when the cells starve. It is thus believed that many DUFs (or proteins of unknown function, PUFs) are only required under certain conditions.
Goodacre et al. identified 238 DUFs in 355 essential proteins (in 16 model bacterial species), most of which represent single-domain proteins, clearly establishing the biological essentiality of DUFs. These DUFs are called "essential DUFs" or eDUFs.
- El-Gebali S, Mistry J, Bateman A, Eddy SR, Luciani A, Potter SC, Qureshi M, Richardson LJ, Salazar GA, Smart A, Sonnhammer EL, Hirsh L, Paladin L, Piovesan D, Tosatto SC, Finn RD (January 2019). "The Pfam protein families database in 2019". Nucleic Acids Research. 47 (D1): D427â€“D432. doi:10.1093/nar/gky995. PMC 6324024. PMID 30357350.
- Bateman A, Coggill P, Finn RD (October 2010). "DUFs: families in search of function". Acta Crystallographica. Section F, Structural Biology and Crystallization Communications. 66 (Pt 10): 1148â€“52. doi:10.1107/S1744309110001685. PMC 2954198. PMID 20944204.
- Punta M, Coggill PC, Eberhardt RY, Mistry J, Tate J, Boursnell C, Pang N, Forslund K, Ceric G, Clements J, Heger A, Holm L, Sonnhammer EL, Eddy SR, Bateman A, Finn RD (January 2012). "The Pfam protein families database". Nucleic Acids Research. 40 (Database issue): D290â€“301. doi:10.1093/nar/gkr1065. PMC 3245129. PMID 22127870.
- Schultz J, Milpetz F, Bork P, Ponting CP (May 1998). "SMART, a simple modular architecture research tool: identification of signaling domains". Proceedings of the National Academy of Sciences of the United States of America. 95 (11): 5857â€“64. Bibcode:1998PNAS...95.5857S. doi:10.1073/pnas.95.11.5857. PMC 34487. PMID 9600884.
- Jaroszewski L, Li Z, Krishna SS, Bakolitsa C, Wooley J, Deacon AM, Wilson IA, Godzik A (September 2009). "Exploration of uncharted regions of the protein universe". PLoS Biology. 7 (9): e1000205. doi:10.1371/journal.pbio.1000205. PMC 2744874. PMID 19787035.
- Mudgal R, Sandhya S, Chandra N, Srinivasan N (July 2015). "De-DUFing the DUFs: Deciphering distant evolutionary relationships of Domains of Unknown Function using sensitive homology detection methods". Biology Direct. 10 (1): 38. doi:10.1186/s13062-015-0069-2. PMC 4520260. PMID 26228684.
- Goodacre NF, Gerloff DL, Uetz P (December 2013). "Protein domains of unknown function are essential in bacteria". mBio. 5 (1): e00744â€“13. doi:10.1128/mBio.00744-13. PMC 3884060. PMID 24381303.
- HÃ¤user R, Pech M, Kijek J, Yamamoto H, Titz B, Naeve F, Tovchigrechko A, Yamamoto K, Szaflarski W, Takeuchi N, Stellberger T, Diefenbacher ME, Nierhaus KH, Uetz P (2012). Hughes D (ed.). "RsfA (YbeB) proteins are conserved ribosomal silencing factors". PLoS Genetics. 8 (7): e1002815. doi:10.1371/journal.pgen.1002815. PMC 3400551. PMID 22829778.
"DUF" families are annotated with the Domain of unknown function Wikipedia article. This is a general article, with no specific information about individual Pfam DUFs. If you have information about this particular DUF, please let us know using the "Add annotation" button below.
Domain of unknown function (DUF2019) Provide feedback
Protein of unknown function found in bacteria.
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.
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Tetratricopeptide-like repeats are found in a numerous and diverse proteins involved in such functions as cell cycle regulation, transcriptional control, mitochondrial and peroxisomal protein transport, neurogenesis and protein folding.
The clan contains the following 252 members:14-3-3 AAR2 Aconitase_B_N Adaptin_N Alkyl_sulf_dimr ANAPC3 ANAPC5 ANAPC8 Apc1_MidN APC_rep API5 Aquarius_N Arm Arm_2 Arm_3 Arm_vescicular Atx10homo_assoc B56 BAF250_C BRO1 BTAD CAS_CSE1 ChAPs CHIP_TPR_N CID CLASP_N Clathrin Clathrin-link Clathrin_H_link Clathrin_propel Cnd1 Cnd1_N Cnd3 CNOT1_CAF1_bind CNOT1_HEAT_N CNOT1_TTP_bind Coatomer_E Cohesin_HEAT Cohesin_load ComR_TPR COPI_C CPL CRM1_C CRM1_repeat CRM1_repeat_3 Cse1 CTK3 CTNNBL Cullin DHR-2_Lobe_A DHR-2_Lobe_C DIL DNA-PKcs_N DNA_alkylation DNAPKcs_CC1-2 DNAPKcs_CC3 DNAPKcs_CC5 Dopey_N Drf_FH3 Drf_GBD DUF1822 DUF2019 DUF2225 DUF3385 DUF3458_C DUF3730 DUF3856 DUF4042 DUF4704 DUF5071 DUF5106 DUF5588 DUF5691 DUF6340 DUF6377 DUF6584 DUF924 E_motif EAD11 eIF-3c_N ELMO_ARM EST1 EST1_DNA_bind FA_FANCE FANCF FANCI_HD1 FANCI_HD2 FANCI_S1 FANCI_S1-cap FANCI_S2 FANCI_S3 FANCI_S4 FAT Fes1 Fis1_TPR_C Fis1_TPR_N Focadhesin Foie-gras_1 GET4 GLE1 GUN4_N HAT HEAT HEAT_2 HEAT_EZ HEAT_PBS HEAT_UF HemY_N HMW1C_N HPS6_C HrpB1_HrpK HSM3_C HSM3_N Hyccin IBB IBN_N IFRD Iml2-TPR_39 Importin_rep Importin_rep_2 Importin_rep_3 Importin_rep_4 Importin_rep_5 Importin_rep_6 Insc_C Ints3_N KAP Kinetochor_Ybp2 Laa1_Sip1_HTR5 Leuk-A4-hydro_C LRV LRV_FeS MA3 Mad3_BUB1_I MAP3K_TRAF_bd MIF4G MIF4G_like MIF4G_like_2 MIX MMS19_C Mo25 MRP-S27 Mtf2 MUN NatA_aux_su Neurobeachin Neurochondrin Nic96 Nipped-B_C Not1 Nro1 NSF Paf67 ParcG PAT1 PC_rep PDS5 Peptidase_M9_N PHAT PI3Ka PknG_TPR PPP5 PPR PPR_1 PPR_2 PPR_3 PPR_long PPTA Proteasom_PSMB PUF PUL RAI16-like Rapsyn_N Rcd1 RIH_assoc RINT1_TIP1 RIX1 RNPP_C RPM2 RPN6_N RPN7 RYDR_ITPR Sel1 SHNi-TPR SIL1 SLT_L SNAP SPO22 SRP_TPR_like ST7 STAG Suf SusD-like SusD-like_2 SusD-like_3 SusD_RagB SYCP2_ARLD SYMPK_PTA1_N TAF1_subA TAF6_C TAL_effector TAP42 TAtT Tcf25 TIP120 TOM20_plant TPR-S TPR_1 TPR_10 TPR_11 TPR_12 TPR_14 TPR_15 TPR_16 TPR_17 TPR_18 TPR_19 TPR_2 TPR_20 TPR_21 TPR_22 TPR_3 TPR_4 TPR_5 TPR_6 TPR_7 TPR_8 TPR_9 TPR_MalT Tra1_ring TRF TTC7_N Type_III_YscG UNC45-central Upf2 Uso1_p115_head V-ATPase_H_C V-ATPase_H_N Vac14_Fab1_bd Vitellogenin_N Vps16_C Vps35 Vps39_1 VPS53_C W2 Wap1 WSLR Wzy_C_2 Xpo1 YcaO_C YfiO Zmiz1_N
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...
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
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.
|Number in seed:||7|
|Number in full:||130|
|Average length of the domain:||100.80 aa|
|Average identity of full alignment:||28 %|
|Average coverage of the sequence by the domain:||75.82 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -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
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.
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 DUF2019 domain has been found. There are 1 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.
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