Construction of Trichosanthin Mutant R122G and Its Activity Study.

AGG, the codon of 122 Arg of trichosanthin (TCS) was mutated to GGG (Gly) by U-DNA site-directed mutagenesis. The mutant TCS was expressed and purified from the supernatant of host cells, its activities were assayed and compared with expressed wild-type TCS. The results showed that the R122G TCS was still active as a RNA N-glycosidase but its ability to inhibit protein synthesis was 160-fold less than that of wild-type TCS, its abortifacient ability on mid-term gestated mice reduced from 100% to 9.3%, which suggested that 122 Arg was indirectly involved in the catalysis, and it played an important role in its bioactivities.