Tryptophanyl-tRNA synthetases are essential enzymes that catalyze the aminoacylation of tRNA(trp) with tryptophan, an essential function of the protein synthesis machinery of the cell. Two forms of tryptophanyl-tRNA synthetase exist: a cytoplasmic form, named TrpRS (also known as WARS), and a mitochondrial form, named WARS2. In normal cells, human TrpRS exists as a full length form and as a truncated form designated mini TrpRS, which is produced by alternative splicing. Expression of mini TrpRs is highly stimulated in human cells by the addition of IFN-gamma. Although both human full-length TrpRS and mini TrpRS are enzymatically active in aminoacylation, they differ in angiostatic activity. The gene encoding human TrpRS maps to chromosome 14q32.31 and the gene encoding human WARS2 maps to chromosome 1p13.3-p13.1. The first 18 amino acids of WARS2 constitute the mitochondrial localization signal sequence.
