Respuesta :
Eukaryotic Initiation:
1) elF3 and elF6 bind to the small and large ribosomal subunits respectively to prevent them from binding to each other without mRNA
2) Ternary complex is formed.
3) Preinitiation complex is formed.
4) Cells can regulate protein synthesis by phosphorylating a serine residue on the elF2 bound to GDP. The phosphorylated complex is unable to exchange the bound GDP for GTP and cannot bind met-tRNA (iMet), thus inhibiting protein synthesis.
5) As the mature mRNA is transported from the nucleus into the cytoplasm, initiation factors (IF4s) for protein synthesis binds to the 5'cap.
6) The preinitiation complex binds to the mRNA-elF4E complex to form the initiation complex through an interaction of the elF4G subunit and elF3. The initiation complex then scans along the mRNA to look for the Kozak sequence containing the first AUG.
7) The helicase elF4A, which is activated by elF4B, uses ATP to unwind RNA structures.
8) Scanning stops as the met-tRNAimet anticodon recognizes the AUG codon (Kozack sequence).
9) elF2-GTP hydrolyzes to eIF2-GDP, an irreversible step that prevents further scanning.
10) The eIFs dissociate.
11) elF5 helps bring in 60S-elF6 ; GTP is hydrolized and the IFs are released.
12) Met- tRNAimet positioned at the P site.
Hope this helps!!!