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Domain of unknown function

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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.

Conservation

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.[4] However, when it was deleted in Escherichia coli no obvious phenotype was obvious. 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 becomes relevant when the cells starve.

Essential DUFs (eDUFs)

Although the functions of most DUFs are unknown by definition, many DUFs are essential. This has been shown by an analysis of essential proteins that contain DUFs, often as their only domain. These DUFs are called "essential DUFs" or eDUFs.[5]

References

  1. ^ Bateman A, Coggill P, Finn RD (2010). "DUFs: families in search of function". Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 66 (Pt 10): 1148–52. doi:10.1107/S1744309110001685. PMC 2954198. PMID 20944204. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  2. ^ Schultz J, Milpetz F, Bork P, Ponting CP (1998). "SMART, a simple modular architecture research tool: identification of signaling domains". Proc. Natl. Acad. Sci. U.S.A. 95 (11): 5857–64. doi:10.1073/pnas.95.11.5857. PMC 34487. PMID 9600884. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  3. ^ Jaroszewski L, Li Z, Krishna SS; et al. (2009). "Exploration of uncharted regions of the protein universe". PLoS Biol. 7 (9): e1000205. doi:10.1371/journal.pbio.1000205. PMC 2744874. PMID 19787035. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
  4. ^ Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 22829778, please use {{cite journal}} with |pmid= 22829778 instead.
  5. ^ Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 24381303, please use {{cite journal}} with |pmid= 24381303 instead.
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