Purification and characterization of novel ribosome inactivating proteins, alpha- and beta-pisavins, from seeds of the garden pea Pisum sativum.

Two ribosome inactivating proteins designated alpha- and beta-pisavins were isolated from seeds of the garden pea Pisum sativum var. arvense Poir with a procedure involving affinity chromatography on Affi-gel Blue gel, immobilized metal ion affinity chromatography on Iminodiacetic acid-agarose, cation exchange chromatography on Resource-S, and gel filtration on Superose 12. alpha- and beta-pisavins are nonglycoproteins with a molecular weight of 20.5 kDa and 18.7 kDa respectively. The sequences of the first sixty N-terminal amino acids of alpha- and beta-pisavins were identical. In isoelectric focusing these two proteins merged into one band with a pI greater than 9.3. Inhibition of protein synthesis by a rabbit reticulocyte lysate system was achieved at an IC50 of approximately 0.5 nM. Activity of the proteins toward tRNA was observed. The proteins acted on ribosomal RNA through its RNA N-glycosidase activity to release an Endo's fragment, and converted the conformation of DNA from supercoiled and circular forms into a linear form.