Primary structure of beta-momorcharin, a ribosome-inactivating protein from the seeds of Momordica Charantia Linn (Cucurbitaceae)

The complete amino acid sequence of beta-momorcharin, a ribosome-inactivati ng protein from the seeds of Momordica charantia Linn (Cucurbitaceae) has b een determined. This has been done by the sequence analysis of peptides obt ained by enzymatic digestion with trypsin, chymotrypsin and S. aureus V8 pr otease, as well as by chemical cleavage with BNPS-skatole. The protein cons ists of 249 amino acid residues containing one asparagine -linked sugar gro up attached to the site of Asn 5 1 and has a calculated relative molecular mass of 28,452 Da without addition of the carbohydrate. Comparison of this sequence with those of trichosanthin and other ribosome-inactivating protei ns from different species of plants shows a significant homology with each other. Regarding the similarity of their biological properties, an active d omain of these proteins has been predicted here.