Ribosome inactivating proteins: Enzymes in search of biological function

Ribosome-inactivating proteins (RIPs) are enzymes (N-glycosidases classified as rRNA N-glycohydrolases, EC 3.2.2.22), mostly of plant origin, but also bacterial, fungal and algal which cause irreversible inhibition protein biosynthesis carried out by ribosomes superior organisms some bacteria. The enzymatic activity consists specific depurination that renders them unable to interact with elongation factor 2 in eukaryotes G prokaryotes. best-known RIPs, ricin abrin, consisting two polypeptide chains (type 2), an chain a lectin for D-galactose galactosides, extremely toxic because they can be internalised cells binding plasma membrane receptors, entering the cytoplasm, reaching Golgi apparatus, then rough endoplasmic reticulum, where transferred cytosol there inactivate ribosomes. most abundant RIPs possess only one 1) do not toxicity abrin. Their biological function plants is currently unknown, although different hypotheses have been proposed their mediation stress response against pathogens. found interesting application construction immunotoxins conjugates experimental cancer therapy. formulation into nanoparticles, has used optimize biopharmaceutical pharmacokinetic properties diagnostic purposes. Keywords: RIP; enzyme; function; inmunotoxin; drug targeting