Saporin is a ribosome-inactivating protein (RIP) of type I. This monomeric RNA N-glycosidase purified from seeds of the plant Saponaria officinalis also known as Soapwort, is capable of specific depurination of eukaryotic ribosomes thus arresting protein synthesis. No ligand has been identified in saporin hence its inability to transverse the cell membrane. Due to its toxicity and stability of the structure, saporin has proven extremely useful for construction of immunotoxins.
