Characterization of pokeweed antiviral protein binding to mRNA cap analogs: competition with nucleotides and enhancement by translation initiation factor iso4G.

Pokeweed antiviral protein (PAP) is a type I ribosomal inactivating protein (RIP). PAP binds to and depurinates the sarcin/ricin loop (SRL) of ribosomal RNA resulting in the cessation of protein synthesis. PAP has also been shown to bind to mRNA cap analogs and depurinate mRNA downstream of the cap structure.