Purification and Characterization of Trichokirin-S1, a Novel Ribosome-inactivating Peptide from Seeds of Trichosanthes kirilowii

A novel peptide from the seeds of Trichosanthes kirilowii, trichokirin-S1, was purified by extraction of protein body, ammonia sulfate precipitation, Blue-gel affinity chromatography, FPLC Mono S ion exchange chromatography and Superose12 gel filtration chromatography. Its molecular weight was determined to be 11 426 by MALDI-TOF MS analysis. Its reaction mechanism to inactive ribosome was the same as that of the ribosome-inactivating protein trichosanthin, a rRNA N-glycosidase. The purified trichokirin-SI showed a strong inhibitory activity on protein synthesis in cell-free rabbit reticulocyte lysate system, with IC50 of 0.7 nmol/L. Therefore, trichokirin-SI may be a promising and efficient toxin moiety of immunotoxins.