A new purification scheme, involving two successive ion exchange chromatographic steps on DEAE-cellulose and Mono-S FPLC, was developed for the isolation of the ribosome-inactivating proteins, α- and β-momorcharins, from the Chinese herb Kuquazi (seeds of Momordica charantia). This simple and rapid procedure yielded 3.1 and 1.7 mg of α- and β-momorcharins, respectively, from 2.5 g of decorticated seeds in only two days. The N-terminal amino acid sequence of β-momorcharin was found to be DVNFDLSTATAKTYTKFIED. It differed from that of α-momorcharin (DVSFRLSGADPRSYGMFIKD) in 10 out of the 20 positions investigated. Like other ribosome-inactivating proteins, the purified momorcharins showed specific N-glycosidase activity at nanomolar concentrations, when rRNA from rabbit reticulocyte lysate was used as substrate. The N-glycosidase activity of both momorcharins was optimal at pH 7, not inhibited by K+ and not appreciably affected by NH4+. The activity of α-momorcharin was not drastically altered by Mn2+ but (1-10 mM) Mn2+ inhibited the activity of β-momorcharin by about 40%.
Scopus Subject Areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)
- Momordica charantia
- Ribosome-inactivating proteins