Elongation of Translation

• 2 adjacent sites on ribosome: P (Peptide) and A (Amino Acid) site
• A site accepts a new tRNA-AA
• P site holds existing chain
• peptide transferred from P site tRNA to A-site AA
• enzyme activity is in ribosomal RNA (ribozyme)
• also required: Energy (GTP) and elongation factors

 

Fig. 18. Elongation of translation

Termination of Translation

• reach a "stop codon" UAG, UAA, or UGA
• no t-RNAs bind
• instead, specific   release factors   required
• Net cost of translation: 4 phosphate bonds/amino acid added.

 

Fig. 19. Termination of translation

NOTE : Typical RNA polymerization rate (~ 40 nts/second at 37°C in bacteria - close to translation rate of about ~15 aa/second).

 

Fig. 20. The complete process of translation