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PROSITE documentation PDOC51644
OST-type HTH domain profile


The OST-HTH (Oskar-TDRD5/TDRD7 HTH) [1] or LOTUS (after Limkain-b1, Oskar and TUdor-containing proteins 5 and 7) [2] domain is a motif of about 80 amino acids and is likely to adopt a winged helix-turn-helix (wHTH) fold, which is characterized by a core 3-stranded HTH with a C-terminal extension of two strands. The OST-HTH domain is primarily found in eukaryotes and bacteria with very rare occurences in archaea that appear to be relatively late lateral transfers of bacterial versions.

The OST-HTH domain is likely to bind RNA with a potential specificity for double-standed RNA (dsRNA) and might have key role in the assembly and localization of RNA-protein complexes with important post-transcriptional regulatory functions.

Some proteins known to contain a OST-HTH domain are listed below:

  • Animal Limkain-b1 (LKAP).
  • Vertebrate Tudor domain-containing protein 5 (TDRD5), required during spermiogenesis to participate in the repression transposable elements and prevent their mobilization, which is essential for the germline integrity.
  • Vertebrate Tudor domain-containing protein 7 (TDRD7), probably acts by binding to specific mRNAs and regulating their translation.
  • Drosophila maternal effect protein oskar (osk), organizes the germ plasm and directs localization of the posterior determinant nanos.

The profile we developed covers the entire OST-HTH domain.

Last update:

May 2012 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

HTH_OST, PS51644; OST-type HTH domain profile  (MATRIX)


1AuthorsAnantharaman V. Zhang D. Aravind L.
TitleOST-HTH: a novel predicted RNA-binding domain.
SourceBiol. Direct 5:13-13(2010).
PubMed ID20302647

2AuthorsCallebaut I. Mornon J.P.
TitleLOTUS, a new domain associated with small RNA pathways in the germline.
SourceBioinformatics 26:1140-1144(2010).
PubMed ID20305267

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