PROSITE documentation PDOC00033

'Homeobox' engrailed-type protein signature

Most proteins which contain a 'homeobox' domain can be classified [1,2], on the basis of their sequence characteristics, in three subfamilies: engrailed, antennapedia and paired. Proteins currently known to belong to the engrailed subfamily are:

• Drosophila segmentation polarity protein engrailed (en) which specifies the body segmentation pattern and is required for the development of the central nervous system.
• Drosophila invected protein (inv).
• Silk moth proteins engrailed and invected, which may be involved in the compartmentalization of the silk gland.
• Honeybee E30 and E60.
• Grasshopper (Schistocerca americana) G-En.
• Mammalian and birds En-1 and En-2.
• Zebrafish Eng-1, -2 and -3.
• Sea urchin (Tripneusteas gratilla) SU-HB-en.
• Leech (Helobdella triserialis) Ht-En.
• Caenorhabditis elegans ceh-16.

Engrailed homeobox proteins are characterized by the presence of a conserved region of some 20 amino-acid residues located at the C-terminal of the 'homeobox' domain. As a signature pattern for this subfamily of proteins, we have used a stretch of eight perfectly conserved residues in this region.