Isolation and characterization of a new ribosome inactivating protein, momorgrosvin, from seeds of the monk's fruit Momordica grosvenorii

Momorgrosvin, a single-chained glycoprotein with a molecular weight of 27.7 kilodaltons and an isoelectric point of about 9 was isolated from the seeds of Momordica grosvenorii (Family Cucurbitaceae). The isolation procedure entailed acetone precipitation, affinity chromatography on Hi Trap Blue, cation exchange chromatography on Resource S and size exclusion chromatography on Superose 12. The sequence of the first eighteen N-terminal amino acid residues of momorgrosvin exhibited homology to those of RIPs from other Momordica species. Momorgrosvin inhibited protein synthesis in the rabbit reticulocyte lysate system with an IC50 of 0.3 nM and displayed RNA N-glycosidase activity giving rise to the diagnostic Endo's band at a concentration as low as 9 nM. The protein acted on tRNA to produce acid-soluble uv-absorbing species.