Protein Synthesis: Translation Process

Overview

Translation is the synthesis of a protein from an mRNA template. This biological process involves several key molecules and is divided into three stages: initiation, elongation, and termination.

Key Molecules Involved

• mRNA
  • Contains codons encoding specific amino acids
  • Features:
    • Poly-A tail at the 3' end
    • Methylated cap at the 5' end
• Ribosome Subunits
  • Small subunit
  • Large subunit
• tRNA
  • Contains an anti-codon complementary to the mRNA codon
  • Carries the corresponding amino acid
• Release Factor

Stages of Translation

1. Initiation

• Begins when the small ribosomal subunit attaches to the 5' cap of the mRNA.
• The small subunit moves to the translation initiation site.
• The first tRNA binds to the mRNA codon AUG, which typically encodes for methionine.
• The large ribosomal subunit binds forming the peptidyl (P) site and aminoacyl (A) site.
  • The first tRNA occupies the P site.

2. Elongation

• The second tRNA enters the A site, which is complementary to the second mRNA codon.
• Methionine is transferred to the amino acid on the A site tRNA.
• The first tRNA exits.
• The ribosome translocates along the mRNA, and new tRNAs continue to enter.
• The growing polypeptide chain is continually transferred to the A site tRNA.

3. Termination

• Occurs when a stop codon is encountered in the A site.
• A release factor enters the A site, terminating the translation.
• The ribosome dissociates, and the newly formed protein is released.

Conclusion

The translation process efficiently synthesizes proteins by decoding the mRNA template in a sequential manner, involving specific interactions among mRNA, ribosomes, tRNA, and release factors.