Characterization of Type 1 ribosome inactivating proteins in edible plants

The ribosome inactivating proteins (RIPs) from plants possess RNA N-glycosidase activity that depurinates the major rRNA, thus damaging ribosome in an irreversible manner and arresting protein synthesis. RIPs occur in fungi, bacteria and plants and are abundant in angiosperms, where they appear to have defensive role. RIPs are presently classified as rRNA N-glycosidase in the enzyme nomenclature (EC 3.2.2.22) and do exhibit other enzymatic activities such as ribonuclease and deoxyribonuclease activities. RIPs are classified into two groups based on their difference in their primary structure. Type I RIPs consist of a single polypeptide chain of approximately 26–35 kDa that possess an RNA N-glycosidase activity. These proteins have attracted a great deal of attention because of their anti-viral, anti-tumor, and anti-microbial activities, which is useful in medical research and development. Here, we describe isolation of a novel protein from Momordica sp, a highclimbing vine from family Cucurbitaceae which is native to the tropical regions of Africa, Asia, Arabia and Caribbean. The purified protein has been verified by SDS-PAGE and mass spectrometry to contain only single chain Type-1 ribosome inactivating proteins (RIPs). With present experiments, we determined the presence of RIPs in edible plant materials, including some that are eaten raw by human beings. The novel protein is further characterized to validate its therapeutic potential.