E site

Definition

The e site, or exit site, is one of the three key binding sites on the ribosome involved in the process of translation. It is specifically the location where the tRNA, after having donated its amino acid to the growing polypeptide chain, exits the ribosome. This site plays a crucial role in ensuring that the translation process continues smoothly by allowing tRNAs to leave the ribosome after their job is done, maintaining the efficiency of protein synthesis.

5 Must Know Facts For Your Next Test

1. The e site is crucial for maintaining the flow of translation by allowing used tRNAs to exit, thus making room for new tRNAs to enter.
2. The e site is located on the large subunit of the ribosome, opposite the A and P sites.
3. tRNA binds to the A site, transfers its amino acid to the polypeptide chain at the P site, and then moves to the e site before exiting.
4. During translation termination, a stop codon is reached, leading to release factors entering the A site, which can influence tRNA release from the e site.
5. Proper functioning of the e site is essential for high fidelity and efficiency in protein synthesis, preventing potential errors in translation.

Review Questions

• How does the e site contribute to the overall efficiency of protein synthesis during translation?
  • The e site contributes to protein synthesis efficiency by allowing tRNA molecules to exit after delivering their amino acids. This exit ensures that there is continuous availability of space for new tRNAs to enter at the A site. By facilitating this cycle, the e site helps maintain a rapid and effective translation process, preventing bottlenecks and ensuring that protein chains are assembled quickly.
• Discuss how interactions between the e site and other ribosomal sites impact translation accuracy and speed.
  • Interactions between the e site and other sites on the ribosome, particularly the A and P sites, are vital for ensuring both accuracy and speed in translation. After tRNA donates its amino acid at the P site, it moves to the e site for exit. If tRNAs do not exit properly due to issues with binding or conformational changes in these sites, it could lead to stalled translation and potential errors in protein synthesis. Thus, efficient coordination among these sites is essential for maintaining high fidelity during protein assembly.
• Evaluate the significance of the e site in relation to ribosomal function during translation termination.
  • During translation termination, the role of the e site becomes especially significant as it interacts with release factors that recognize stop codons. When a stop codon enters the A site, these release factors promote hydrolysis of the bond between tRNA and its polypeptide chain at the P site. This action not only allows for proper release of newly synthesized proteins but also influences how tRNA exits through the e site. Hence, this interaction is crucial for ensuring that proteins are released correctly and that ribosomes can be recycled for subsequent rounds of translation.

Related terms

ribosome: A complex molecular machine found within all living cells that facilitates the synthesis of proteins by translating messenger RNA (mRNA) into amino acid sequences.

A site: The aminoacyl site on the ribosome where incoming tRNA molecules, carrying new amino acids, bind before being added to the growing polypeptide chain.

P site: The peptidyl site on the ribosome that holds the tRNA carrying the growing polypeptide chain during translation.