IDENTIFICATION OF A BIOLOGICAL INACTIVE COMPLEX FORM OF POKEWEED ANTIVIRAL PROTEIN

Pokeweed antiviral protein (PAP) inactivates both eukaryotic and proka ryotic ribosomes via a specific depurination of rRNA, The sensitivity of pokeweed ribosomes to PAP implies the existence of a mechanism to p rotect the plant. Using monoclonal antibodies specific to PAP, a prote in complex (PAPi) which contained PAP was identified in leaf extract, In this complex, the enzymatic activity of the toxin was strongly inhi bited, This protein complex had a pi lower than that of PAP and was se parated from free PAP by a preparative native gel electrophoresis, PAP i had an apparent molecular mass of 57 kDa and was dissociated by heat ing for 5 min at 80 degrees C or by treatment by alkaline or acidic pH or by 7 M urea, The other components involved in the complex remain u nknown. (C) 1997 Federation of European Biochemical Societies.