3. Translation process

3.2 Initiation of translation

3.2.2 Identification of the start codon

Each mRNA may contain several AUG codons (Met is often found inside the protein, not only at the beginning).

How is the right AUG correctly identified?

In eucaryotes

  • The initiation complex recognizes, by way of the cap, the 5‘ end of the mRNA.

  • It then moves along the mRNA towards the 3’ end, until it reaches the 1st AUG.

  • The nucleotides flanking this AUG may or may not facilitate the initiation complex to stop. The optimum consensus sequence (or Kozak sequence) is ACC AUG G.

Initiation of translation

  • In rare cases, if the 1st AUG is not correctly recognized, the complex moves forward up to the 2nd AUG.