Translation in eukaryotes vs prokaryotes

Translation in eukaryotes is very similar to that in prokaryotes. The biggest differences are seen in initiation. Prokaryotes have no internal membrane-bound organelles and no nucleus, so both transcription and translation happen in the same compartment. This allows for the simultaneous transcription and translation illustrated in Figure 10. But in eukaryotes, transcription happens in the nucleus, and translation happens on ribosomes in the cytoplasm – transcription and translation, therefore, can’t both act on the same mRNA at the same time.

Eukaryotes also do not have a Shine-Dalgarno sequence. Instead, the 5’ cap serves as a ribosome binding site, and the ribosome scans toward the 3’ end of the mRNA until a start codon is encountered. fMet is not used as an initiator amino acid; all eukaryotic polypeptides begin with methionine^[1]. However, there is a dedicated initiator tRNA_i^Met that is distinct from the methionine tRNA used during elongation^[2].

The prokaryotic initiation factors, elongation factors, and release factors all have eukaryotic homologs that make prokaryotic and eukaryotic translation very similar mechanistically.