New ribosome-inactivating proteins from seeds and fruits of the bitter gourd Momordica charantia

A new ribosome-inactivating protein (RIP) (δ-momorcharin) and a candidate RIP (e-momorcharin) were isolated, respectively, from the seeds and fruits of the bitter gourd Momordica charantia, by affinity chromatography on Affi-gel blue gel and ion exchange chromatography on Mono S with a fast protein liquid chromatography (FPLC) system. Both δ- and e-momorcharins were adsorbed on Affi-gel blue gel and were eluted from the cation exchange Mono S column earlier than α- and β-momorcharins, the two previously reported RIPs, δ- and e-momorcharins possessed a molecular weight of 30 and 24 kDa respectively and inhibited cell-free translation in rabbit reticulocyte lysate with an IC50 of 0.15 and 170 nM. The sequence of the first seven N-terminal amino acids in δ-momorcharin was DVNFGLA, which was different from the N-terminal sequences DVSFRLS and DVNFDLS for α- and β-momorcharins respectively.