A NOVEL TYPE-1 RIBOSOME-INACTIVATING PROTEIN ISOLATED FROM THE SUPERNATANT OF TRANSFORMED SUSPENSION-CULTURES OF TRICHOSANTHES-KIRILOWII

A type-1 ribosome-inactivating protein (RIP) designated TK-35 has been purified from the supernatant of suspension cultures of Agrobacterium rhizogenes-transformed stem sections of Trichosanthes kirilowii. The protein was purified from the supernatant by PerSeptive SH/M cation ex change and Sephadex G-75 S gel permeation chromatography. The protein occurs as a monomer, with a molecular weight of 35,117, and is glycosy lated. A protein translation inhibition assay indicates that TK-35 has an IC50 value of 2.45 nhl and is able to release the rRNA N-glycosida se diagnostic fragment from rabbit reticulocyte lysate. TK-35 is quite thermally stable. Analysis of its N-terminal sequence and two lys-C-p rotease-digested polypeptides (internal) amino acid sequence indicates that this protein is not homologous to trichosanthin and other type-1 RIPs in Cucurbitaceae family.