Single-chain ribosome inactivating proteins from plants depurinate Escherichia coli23S ribosomal RNA

The rRNA N-glycosidase activities of the catalytically active A chains of the heterodimeric ribosome inactivating proteins (RIPs) ricin and abrin, the single-chain RIPs dianthin 30, dianthin 32, and the leaf and seed forms of pokeweed antiviral protein (PAP) were assayed on E. coliribosomes. All of the single-chain RIPs were active on E. coliribosomes as judged by the release of a 243 nucleotide fragment from the 3′ end of 23S rRNA following aniline treatment of the RNA. In contrast, E. coliribosomes were refractory to the A chains of ricin and abrin. The position of the modification of 23S rRNA by dianthin 32 was determined by primer extension and found to be A 2660, which lies in a sequence that is highly conserved in all species.