| Pokeweed antiviral protein (PAP) is a 29 kDa ribosome inactivating protein (RIP), which depurinates the conserved sarcin/ricin loop of large rRNAs.; In this study, I determined that PAP and eIF4E or eIFiso4E do not compete for the cap structure, however, they also do not interact with each other. I have demonstrated for the first time that PAP is able to interact with eukaryotic initiation factors eIF4G and eIFiso4G by far western assay, and yeast two hybrid interaction assays. I have also mapped the PAP binding site on eIFiso4G to be in the C-terminus and potentially within the residues 541--553 of eIFiso4G from truncation studies of eIFiso4G and crosslinking PAP to eIFiso4G followed by MS-MS analysis. Furthermore, I have determined that PAP forms a novel complex with eIF4G and eIFiso4G at the cap structure. These findings show that PAP interacts with key translation initiation factors, however, further studies are required to understand the significance of these interactions in planta. |
