Function
Ribosome inactivating protein (RIP) is a bacterial or plant toxin which inhibits protein synthesis. RIP inactivates the ribosomal 60S subunit by N-glycosidic cleavage which results in releasing a specific adenine from 28S rRNA[1]. Type 1 RIP have a single chain, while type 2 RIP (i.e., ricin, ebulin and nigrin) have two chains. Momorcharin is a RIP isolated from several plants[2]. Trichosanthin is a RIP isolated from snake gourd[3].
Relevance
RIP is being investigated as an immunotoxin for cancer treatment. Besides the anti-tumor activity of RIP, it was shown to have antiviral, antifungal, insecticidal, ribonuclease and deoxyribonuclease activities. Enhanced expression of RIP in plants confers an increased resistance to virus, fungi, insects, drought and salinity. α-momorcharin has potent inhibitory effect on some cancer cells[4].
Structural highlights
The [5]. Water molecules are shown as red spheres.