High-Level Expression and Single-Step Purification of Human Tryptophanyl-tRNA Synthetase

Human trpS gene was cloned into the expression vector pET-24a(+) to yield pET-24a(+)-HTrpRS, which could direct the synthesis of a mammalian derived protein in Escherichia coli BL21-CodonPlus(DE3)-RIL. The vector allows overproduction and single-step purification of His6-tagged human tryptophanyl-tRNA synthetase by the facilitation of metal (Ni2+) chelate affinity chromatography. The expression level of human TrpRS was about 40% of total cell proteins after isopropyl β-d-thiogalactoside induction. The overproduced human TrpRS-His6 could be purified to homogeneity within 2 h and about 24 mg purified enzyme could be obtained from 400 ml cell culture. The His6 tag at C terminus had little effect on the binding ability of its substrates.