Purification and Partial Characterization of S-trichokirin, A New Small Ribosome-inactivating Protein, from Seeds of Trichosanthes kirilowii

TAI Ning-Wen^*, LI Feng, LI Zhen, ZHUANG Da-Huan^*, ZHANG Zu-Chuan^**
( Shanghai Institute of Biochemistry, the Chinese Academy of Sciences, Shanghai 200031, China )

Abstracts    A new small ribosome-inactivating protein named S-trichokirin from the seeds of Trichosanthes kirilowii was purified by ammonia sulfate precipitation, CM-52 ion exchange chromatography, Sephacryl S-100 gel filtration and FPLC Mono S ion exchange chromatography. S-trichokirin has molecular weight about 8 kD, as determined by 15% SDS-PAGE and 15% Tris-Tricine PAGE. It was proved to be a strong basic protein with pI about pH 9.5 by 13.5% acidic PAGE. The reaction mechanism of S-trichokirin is the same as that of trichosanthin, which is an RNA N-glycosidase. It had a strong inhibitory effect on protein biosynthesis in rabbit reticulocyte lysate with IC₅₀ of 1.15×10^-10 mol/L. S-trichokirin may be used as a new efficient moiety of immunotoxin.
Key words    ribosome-inactivating protein；S-trichokirin；RNA N-glycosidase

^*Sericultural Research Institute, the Chinese Academy of Agricultural Sciences, Zhenjiang 212018, China
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