POU domain

Merge|POU_domain |target= |discuss=Talk:#Merger proposal |date=May 2011}}

POU domain is an evolutionary conserved protein domain.

POU proteins are eukaryotic transcription factors containing a bipartite DNA binding domain referred to as the POU domain. The acronym POU (pronounced 'pow') is derived from the names of three mammalian transcription factors, the pituitary-specific Pit-1, the octamer-binding proteins Oct-1 and Oct-2, and the neural Unc-86 from Caenorhabditis elegans. 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. The various members of the POU family have a wide variety of functions, all of which are related to the function of the neuroendocrine system and the development of an organism. Some other genes are also regulated, including those for immunoglobulin light and heavy chains (Oct-2), and trophic hormone genes, such as those for prolactin and growth hormone (Pit-1).

The POU domain is a bipartite domain composed of two subunits separated by a non-conserved region of 15-55 aa. The N-terminal subunit is known as the POU-specific (POUs) domain, while the C-terminal subunit is a homeobox domain. 3D structures of complexes including both POU subdomains bound to DNA are available. 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. The domain may also be involved in protein-protein interactions. The subdomains are connected by a flexible linker. In proteins a POU-specific domain is always accompanied by a homeodomain. Despite of the lack of sequence homology, 3D structure of POUs is similar to 3D structure of bacteriophage lambda repressor and other members of HTH_3 family.

Examples
Human genes encoding proteins containing the Pou domain include:
 * POU1F1;
 * POU2F1;   POU2F2;    POU2F3;
 * POU3F1;   POU3F2;    POU3F3;    POU3F4;
 * POU4F1;   POU4F2;    POU4F3;
 * POU5F1;   POU5F1P1;  POU5F1P3;  POU5F1P4;  POU5F2;
 * POU6F2