the initiation of protein synthesis in eukaryotes

Note that the process is in principle very similar to prokaryotic initiation.  Major differences from prokaryotic initiation are associated with the m⁷G cap of the mRNA and its interaction with the cap-binding protein (CBPI) and eIF4F (CBPII) instead of Shine-Dalgarno sequence-mediated alignment to properly position the first AUG codon in the P site of the ribosome and the absence of initiator tRNA-fMet.

Summary

• Polypeptide synthesis proceeds sequentially from N terminus to C terminus
• Ribosomes read mRNA only in the 5'->3' direction, never in the 3'->5' direction
• Active translation typically occurs on polyribosomes
• Chain elongation links the growing polypeptide to incoming aminoacyl-tRNA
• Three steps are involved in the synthesis of one polypeptide chain of N residues:

1.  INITIATION (1 x)
2.  ELONGATION (N-1 x)
3.  TERMINATION (1 x)

• Initiation in prokaryotes requires:

1.  One empty 70S ribosome
2.  Three initiation factors:  IF1, IF2, IF3
3.  mRNA with Shine-Dalgarno sequence and START codon (AUG)
4.  Initiator fMet-tRNA^fMet
5.  One high-energy phosphate bond from GTP

• Initiation in eukaryotes is similar, but more complicated (no Shine-Dalgarno, no fMet, 10+ eIFs, etc)