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0  structures 259  species 0  interactions 538  sequences 13  architectures

Family: DUF3399 (PF11879)

Summary: Domain of unknown function (DUF3399)

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 "Domain of unknown function". More...

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. There are now over 3,000 DUF families within the Pfam database representing over 20% of known families.[1]

History

The DUF naming scheme was introduced by Chris Ponting, through the addition of DUF1 and DUF2 to the SMART database.[2] 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.

Structure

Structural genomics programmes have attempted to understand the function of DUFs through structure determination. The structures of over 250 DUF families have been solved.[3] This 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.

Frequency and conservation

Protein domains and DUFs in different domains of life. Left: Annotated domains. Right: domains of unknown function. Not all overlaps shown.[4]

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.[4]

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.[5] 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.[5] 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.[5] It is thus believed that many DUFs (or proteins of unknown function, PUFs) are only required under certain conditions.

Essential DUFs (eDUFs)

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.[4]

External links

References

  1. ^ Bateman A, Coggill P, Finn RD (October 2010). "DUFs: families in search of function". Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 66 (Pt 10): 1148–52. PMC 2954198Freely accessible. PMID 20944204. doi:10.1107/S1744309110001685. 
  2. ^ Schultz J, Milpetz F, Bork P, Ponting CP (May 1998). "SMART, a simple modular architecture research tool: identification of signaling domains". Proc. Natl. Acad. Sci. U.S.A. 95 (11): 5857–64. PMC 34487Freely accessible. PMID 9600884. doi:10.1073/pnas.95.11.5857. 
  3. ^ Jaroszewski L, Li Z, Krishna SS, et al. (September 2009). "Exploration of uncharted regions of the protein universe". PLoS Biol. 7 (9): e1000205. PMC 2744874Freely accessible. PMID 19787035. doi:10.1371/journal.pbio.1000205. 
  4. ^ a b c Goodacre, N. F.; Gerloff, D. L.; Uetz, P. (2013). "Protein Domains of Unknown Function Are Essential in Bacteria". MBio. 5 (1): e00744–e00713. PMC 3884060Freely accessible. PMID 24381303. doi:10.1128/mBio.00744-13. 
  5. ^ a b c Häuser, R.; Pech, M.; Kijek, J.; Yamamoto, H.; Titz, B. R.; Naeve, F.; Tovchigrechko, A.; Yamamoto, K.; Szaflarski, W.; Takeuchi, N.; Stellberger, T.; Diefenbacher, M. E.; Nierhaus, K. H.; Uetz, P. (2012). Hughes, Diarmaid, ed. "RsfA (YbeB) Proteins Are Conserved Ribosomal Silencing Factors". PLoS Genetics. 8 (7): e1002815. PMC 3400551Freely accessible. PMID 22829778. doi:10.1371/journal.pgen.1002815. 

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

"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 (DUF3399) Provide feedback

This domain is functionally uncharacterised. This domain is found in eukaryotes. This presumed domain is about 100 amino acids in length. This domain is found associated with PF02214 PF00520.

This tab holds annotation information from the InterPro database.

InterPro entry IPR024587

Potassium channels are the most diverse group of the ion channel family [PUBMED:1772658, PUBMED:1879548]. They are important in shaping the action potential, and in neuronal excitability and plasticity [PUBMED:2451788]. The potassium channel family is composed of several functionally distinct isoforms, which can be broadly separated into 2 groups [PUBMED:2555158]: the practically non-inactivating 'delayed' group and the rapidly inactivating 'transient' group.

These are all highly similar proteins, with only small amino acid changes causing the diversity of the voltage-dependent gating mechanism, channel conductance and toxin binding properties. Each type of K+ channel is activated by different signals and conditions depending on their type of regulation: some open in response to depolarisation of the plasma membrane; others in response to hyperpolarisation or an increase in intracellular calcium concentration; some can be regulated by binding of a transmitter, together with intracellular kinases; while others are regulated by GTP-binding proteins or other second messengers [PUBMED:2448635]. In eukaryotic cells, K+ channels are involved in neural signalling and generation of the cardiac rhythm, act as effectors in signal transduction pathways involving G protein-coupled receptors (GPCRs) and may have a role in target cell lysis by cytotoxic T-lymphocytes [PUBMED:1373731]. In prokaryotic cells, they play a role in the maintenance of ionic homeostasis [PUBMED:11178249].

All K+ channels discovered so far possess a core of alpha subunits, each comprising either one or two copies of a highly conserved pore loop domain (P-domain). The P-domain contains the sequence (T/SxxTxGxG), which has been termed the K+ selectivity sequence. In families that contain one P-domain, four subunits assemble to form a selective pathway for K+ across the membrane. However, it remains unclear how the 2 P-domain subunits assemble to form a selective pore. The functional diversity of these families can arise through homo- or hetero-associations of alpha subunits or association with auxiliary cytoplasmic beta subunits. K+ channel subunits containing one pore domain can be assigned into one of two superfamilies: those that possess six transmembrane (TM) domains and those that possess only two TM domains. The six TM domain superfamily can be further subdivided into conserved gene families: the voltage-gated (Kv) channels; the KCNQ channels (originally known as KvLQT channels); the EAG-like K+ channels; and three types of calcium (Ca)-activated K+ channels (BK, IK and SK) [PUBMED:11178249]. The 2TM domain family comprises inward-rectifying K+ channels. In addition, there are K+ channel alpha-subunits that possess two P-domains. These are usually highly regulated K+ selective leak channels.

The Kv family can be divided into several subfamilies on the basis of sequence similarity and function. Four of these subfamilies, Kv1 (Shaker), Kv2 (Shab), Kv3 (Shaw) and Kv4 (Shal), consist of pore-forming alpha subunits that associate with different types of beta subunit. Each alpha subunit comprises six hydrophobic TM domains with a P-domain between the fifth and sixth, which partially resides in the membrane. The fourth TM domain has positively charged residues at every third residue and acts as a voltage sensor, which triggers the conformational change that opens the channel pore in response to a displacement in membrane potential [PUBMED:10712896]. More recently, 4 new electrically-silent alpha subunits have been cloned: Kv5 (KCNF), Kv6 (KCNG), Kv8 and Kv9 (KCNS). These subunits do not themselves possess any functional activity, but appear to form heteromeric channels with Kv2 subunits, and thus modulate Shab channel activity [PUBMED:9305895]. When highly expressed, they inhibit channel activity, but at lower levels show more specific modulatory actions.

The Shal potassium channel was found in Drosophila melanogaster (Fruit fly). Several vertebrate potassium channels with similar amino acid sequences were subsequently found and, together with the D. melanogaster Shal channel, now constitute the Kv4 family. These channels are the primary subunits contributing to transient, voltage-dependent potassium currents in the nervous system (A currents) and the heart (transient outward current), and are inhibited by free fatty acids [PUBMED:15269337]. This family can be further divided into 3 subfamilies, designated Kv4.1(KCND1), Kv4.2(KCND2) and Kv4.3(KCND3).

This uncharacterised C-terminal domain is associated with the Shal (Kv4) potassium channel.

Domain organisation

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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 (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...

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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
(25)
Full
(538)
Representative proteomes UniProt
(742)
NCBI
(1561)
Meta
(0)
RP15
(110)
RP35
(218)
RP55
(403)
RP75
(475)
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Key: ✓ available, x not generated, not available.

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  Seed
(25)
Full
(538)
Representative proteomes UniProt
(742)
NCBI
(1561)
Meta
(0)
RP15
(110)
RP35
(218)
RP55
(403)
RP75
(475)
Alignment:
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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
(25)
Full
(538)
Representative proteomes UniProt
(742)
NCBI
(1561)
Meta
(0)
RP15
(110)
RP35
(218)
RP55
(403)
RP75
(475)
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.

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 View help on the curation process

Seed source: PFAM-B_3857 (release 23.0)
Previous IDs: none
Type: Family
Sequence Ontology: SO:0100021
Author: Assefa S , Coggill P , Bateman A
Number in seed: 25
Number in full: 538
Average length of the domain: 101.60 aa
Average identity of full alignment: 40 %
Average coverage of the sequence by the domain: 21.14 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 45638612 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 25.0 25.0
Trusted cut-off 25.3 25.2
Noise cut-off 23.5 24.2
Model length: 104
Family (HMM) version: 8
Download: download the raw HMM for this family

Species distribution

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Archea Archea Eukaryota Eukaryota
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