Brent Cornell

    
Initiation

The first stage of translation involves the assembly of the three components that carry out the process (mRNA, tRNA, ribosome)

• The small ribosomal subunit binds to the 5’-end of the mRNA and moves along it until it reaches the start codon (AUG)
• Next, the appropriate tRNA molecule bind to the codon via its anticodon (according to complementary base pairing)
• Finally, the large ribosomal subunit aligns itself to the tRNA molecule at the P site and forms a complex with the small subunit
  
  

    
Elongation

• A second tRNA molecule pairs with the next codon in the ribosomal A site
• The amino acid in the P site is covalently attached via a peptide bond (condensation reaction) to the amino acid in the A site
• The tRNA in the P site is now deacylated (no amino acid), while the tRNA in the A site carries the peptide chain

Translocation

• The ribosome moves along the mRNA strand by one codon position (in a 5’ → 3’ direction)
• The deacylated tRNA moves into the E site and is released, while the tRNA carrying the peptide chain moves to the P site
• Another tRNA molecules attaches to the next codon in the now unoccupied A site and the process is repeated

    
Termination

The final stage of translation involves the disassembly of the components and the release of a polypeptide chain

• Elongation and translocation continue in a repeating cycle until the ribosome reaches a stop codon 
• These codons do not recruit a tRNA molecule, but instead recruit a release factor that signals for translation to stop
• The polypeptide is released and the ribosome disassembles back into its two independent subunits

Translation Summary Animation