A conserved domain of 46 amino acids, called WHEP-TRS has been shown [<cite idref="PUB00001214"/>] to exist in a number of higher eukaryote aminoacyl-transfer RNA synthetases. This domain is present one to sixtimes in the several enzymes. There are three copies in mammalian multifunctional aminoacyl-tRNA synthetase in a region that separates the N-terminal glutamyl-tRNA synthetase domain from the C-terminal prolyl-tRNA synthetase domain, and six copies in the intercatalytic region of the Drosophila enzyme. The domain is found at the N-terminal extremity of the mammalian tryptophanyl-tRNA synthetase and histidyl-tRNA synthetase, and the mammalian, insect, nematode and plant glycyl-tRNA synthetases [<cite idref="PUB00002829"/>]. This domain could contain a central alpha-helical region and may play a role in the association of tRNA-synthetases into multienzyme complexes. WHEP-TRS