The DOMON domain is an 110-125 residue long domain which has been identified in the physiologically important enzyme dopamine β-monooxygenase and in several other secreted and transmembrane proteins from both plants and animals. It has been named after DOpamine β-MOnooxygenase N-terminal domain. The DOMON domain can be found in one to four copies and in association with other domains, such as the Cu-ascorbate dependent monooxygenase domain, the epidermal growth factor domain (see <PDOC00021>), the trypsin inhibitor-like domain (TIL), the SEA domain (see <PDOC50024>), and the Reelin domain. The architectures of the DOMON domain proteins strongly suggest a function in extracellular adhesion [1,2].

The sequence conservation is predominantly centered around patches of hydrophobic residues. The secondary structure prediction of the DOMON domain points to an all-β-strand fold with seven or eight core strands supported by a buried core of conserved hydrophobic residues. There is a characteristic motif with two small positions (Gly or Ser) corresponding to a conserved turn immediately C-terminal to strand three. It has been proposed that the DOMON domain might form a β-sandwich structure, with the strands distributed into two β sheets as is seen in many extracellular adhesion domains such as the immunoglobulin, fibronectin type-III, cadherin and PKD (see <PDOC50093>) domains [1].

Some proteins known to contain a DOMON domain are listed below:

• Mammalian dopamine β-monooxygenase (DM). It is involved in the conversion of dopamine to the catecholamine noradrenaline, a crucial physiological modulator of the sympathetic nervous system, T-cell-mediated immunity and fetal development.
• Drosophila tyramine-β-hydroxylase (TBH), an orthologue of DM. It is needed for the biosynthesis of the neurotransmitter octopamine from tyramine.
• Human brain protein C9orf4.
• Mouse SDR2 protein.
• Botryllus schlosseri PAR protein, a soluble immunoglobulin molecule homologue.
• Caenorhabditis elegans uncharacterized protein C09F9.2.
• Arabidopsis thaliana uncharacterized protein At5g54830.

The profile we developed covers the entire DOMON domain.