The acronym POU is derived from the names of three transcription factors: POU domain genes have been described in organisms as divergent as Caenorhabditis elegans, Drosophila, Xenopus, zebrafish and human but have not been yet identified in plants and fungi.
Comparisons of POU domain genes across the animals suggests that the family can be divided into six major classes (POU1-POU6).
[2] There is a surprisingly high degree of amino acid sequence conservation (37%-42%) of POU homeodomains to the transcriptional regulator comS, the competence protein from the gram positive prokaryote Bacillus subtilis.
Both subdomains contain the structural motif 'helix-turn-helix', which directly associates with the two components of bipartite DNA binding sites, and both are required for high affinity sequence-specific DNA-binding.
[9][10] Human genes encoding proteins containing the POU domain and related pseudogenes include: