Initiation Factors and Capped Mediated 48S Initiation Complex Formation of Protein Synthesis

Initially, initiator tRNA-GTP-eIF2 form a complex and bind to the 40S ribosomal subunit. Subsequent 43S complex formation occures with attachment of eIF1, eIF1A and eIF3. In addition, eIF4A, eIF4B, eIF4F and PABP are involved in ATP-dependent binding to mRNA. The newly bound43S complex is now capable of scanning the mRNA in a 5' to 3' direction in search of an initiation codon. AUG codon discovery allows for eIF5 mediated hydrolysis of the GTP bound to eIF2 and allows the resulting 48S complex to attach to a 60S ribosomal subunit and create a translational functional ribosome (Pestova and Hellen, 2000).