The BSD domain is an about 60-residue long domain named after the BTF2-like transcription factors, Synapse-associated proteins and DOS2-like proteins in which it is found. Additionally, it is also found in several hypothetical proteins. The BSD domain occurs in one or two copies in a variety of species ranging from primal protozoan to human. It can be found associated with other domains such as the BTB domain (see <PDOC50097>) or the U-box in multidomain proteins. The function of the BSD domain is yet unknown [1].

Secondary structure prediction indicates the presence of three predicted α helices, which probably form a three-helical bundle in small domains. The third predicted helix contains neighboring phenylalanine and tryptophan residues - less common amino acids that are invariant in all the BSD domains identified and that are the most striking sequence features of the domain [1].

Some proteins known to contain one or two BSD domains are listed below:

• Mammalian TFIIH basal transcription factor complex p62 subunit (GTF2H1).
• Yeast RNA polymerase II transcription factor B 73 kDa subunit (TFB1), the homologue of BTF2.
• Yeast DOS2 protein. It is involved in single-copy DNA replication and ubiquitination.
• Drosophila synapse-associated protein SAP47.
• Mammalian SYAP1.
• Various Arabidopsis thaliana hypothetical proteins.

The profile we developed covers the entire BSD domain.