Plant ribosome inactivating proteins (RIPs) N-beta-glycosylases which cleave the N-beta-glycosidic bond of adenine in a specific ribosomal RNA sequence, known as Sarcin Ricin Loop (SRL). Most commonly RIPs are single-chain proteins (type 1 RIPs), but some (type 2 RIPs) possess a galactose–specific lectin domain that binds to cell surfaces. The latter RIPs are potent toxins, the best known of which is ricin. RIPs have antiviral and abortifacient activities, and, in a widespread application, can also be linked to antibodies or ligands to form immunotoxins or conjugates specifically toxic to a given type of cell.

Ribotoxin-like proteins (RL-Ps) are a family of specific, monomeric (~15-kDa) ribonucleases found in edible basidiomycetes mushrooms. They inhibit protein synthesis and induce cell death by catalysing the endonucleolytic cleavage of the Sarcin Ricin Loop (SRL) in the large ribosomal RNA. 

They act as highly specific hydrolases, cleaving a single phosphodiester bond within the ribosomal SRL, which is vital for binding elongation factors. Due to their cytotoxic activity -particularly against tumour cell lines and pathogenic fungi - they are studied for potential anticancer therapies and as bioinsecticides.