Tyrosyl-tRNA synthetase, also known as YARS, belongs to the class I tRNA synthetase family. YARS is essential enzyme that catalyze the aminoacylation of tRNATrp with tryptophan, an essential function of the cell's protein synthesis machinery. Expression of YARS is highly stimulated in human cells by the addition of IFN-gamma. Recombinant human YARS protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.