1. eIF1 Met-tRNAi eIF3 eIF5 eIF1 eIF1A GTP GTP GTP eIF3 eIF2 eIF2 eIF2 40S TC eIF5 MFC eIF1 GTP eIF1A eIF4G eIF3 eIF2 eIF4E eIF5 43S AAAAAA m7Gppp Recruitment to mRNA 5’end What structural changes render 40S recruitment- enabled? mRNA AAAAAA eIF4E Pab1 eIF1A eIF4G eIF1 eIF2 eIF3 eIF5 eIF4G 48S eIF1A AUG eIF1 eIF2 eIF3 ATP ADP + Pi eIF5 Scanning Supplementary Figure 5 A cartoon of the translation initiation pathway. This serves to indicate the involvement of the large number of eukaryotic initiation factors (eIFs, thus forming 43S). How do these eIFs facilitate entry of the 5’end of the mRNA into the mRNA channel of the 40S subunit? After recruitment of the 43S pre-initiation complex to the 5’end of the mRNA, it scans progressively along the 5’UTR in search of a start codon. This scanning process is facilitated by helicase-catalysed unwinding that is dependent on ATP hydrolysis. MFC = multifactor complex (eIF1, eIF2, eIF3, eIF5)