Isolation and identification of foetidissimin: a novel ribosome-inactivating protein from Cucurbita Foetidissima

Abstract

Cucurbita foetidissima was analyzed for ribosome-inactivating proteins, which potentially could be used as specific anticancer and antiviral agents, and in plant protection. A novel type II RIP, foetidissimin, was found and characterized in this study. Foetidissimin was isolated from the roots of C. foetidissima by size exclusion and ion exchange chromatographic methods. A non-radioactive protein synthesis inhibition assay was used to guide the separation. The molecular weight of the dimeric protein is 63 kDa and the two chains are held together by non-covalent interactions. Using a non-radioactive protein synthesis inhibition assay, foetidissimin inhibited cell-free translation in rabbit reticulocyte lysate with an LC 50 of 25.9 nM. The N-terminal sequence analysis of the first 14 amino acids showed that the A chain of foetidissimin shares 88% similarity with α-trichosanthin, a type I RIP, and 72% similarity with A chain of nigrin F, a type II RIP.