Kirkiin: A New Toxic Type 2 Ribosome-Inactivating Protein from the Caudex of Adenia kirkii

Ribosome-inactivating proteins (RIPs) are plant toxins that irreversibly damage ribosomes and other substrates, thus causing cell death. RIPs classified in type 1 RIPs, single-chain enzymatic proteins, 2 consisting of active A chains, similar to linked lectin B which enable the rapid internalization toxin into cell. For this reason, many very cytotoxic, ricin, volkensin stenodactylin being most toxic ones. From caudex Adenia kirkii (Mast.) Engl., a new RIP, named kirkiin, was purified by affinity chromatography on acid-treated Sepharose CL-6B gel filtration. The lectin, with molecular weight about 58 kDa, agglutinated erythrocytes inhibited protein synthesis cell-free system at low concentrations. Moreover, kirkiin able depurinate mammalian yeast ribosomes, but it showed little or no activity nucleotide substrates. In neuroblastoma cells, induced apoptosis doses pM range. biological characteristics make potential candidate for several experimental pharmacological applications both alone local treatments as component immunoconjugates systemic targeting neurodegenerative studies cancer therapy.