E site

Definition

The E site, or exit site, is one of the three binding sites on the ribosome during protein synthesis. It is the location where deacylated tRNA, which has given up its amino acid to the growing polypeptide chain, exits the ribosome after the peptide bond formation. Understanding the function of the E site is crucial for grasping how translation efficiently operates to synthesize proteins based on the genetic code.

5 Must Know Facts For Your Next Test

1. The E site plays a critical role in ensuring that tRNAs exit the ribosome after their amino acids have been added to the polypeptide chain.
2. Proper function of the E site is vital for maintaining the efficiency and accuracy of protein synthesis.
3. The movement of tRNAs between the A site, P site, and E site is facilitated by elongation factors during translation.
4. The E site ensures that only empty tRNAs are released from the ribosome, preventing any premature errors in protein assembly.
5. During the termination phase of translation, the ribosome disassembles and releases all bound tRNAs from their respective sites, including the E site.

Review Questions

• How does the E site contribute to the overall process of translation?
  • The E site contributes to translation by providing a designated area for deacylated tRNA to exit after it has released its amino acid into the growing polypeptide chain. This exit process is essential for recycling tRNAs back into the cytoplasm for recharging with new amino acids. By facilitating this step, the E site ensures that translation can continue efficiently without accumulating unnecessary tRNA molecules within the ribosome.
• Discuss how the interaction between the A site, P site, and E site influences protein synthesis.
  • The interaction between the A site, P site, and E site is crucial for maintaining a smooth flow of tRNAs and amino acids during protein synthesis. The A site receives incoming charged tRNAs with new amino acids, while the P site holds onto tRNAs with growing polypeptides. After peptide bond formation occurs between amino acids at the P site and A site, deacylated tRNAs move to the E site for exit. This coordinated movement ensures that each step of translation occurs correctly and without interruptions.
• Evaluate the importance of the E site's function in relation to potential errors in protein synthesis.
  • The function of the E site is critically important in preventing errors during protein synthesis. If deacylated tRNA were not efficiently released from the E site, it could lead to overcrowding within the ribosome and hinder subsequent rounds of translation. This could increase the chances of misincorporating incorrect amino acids or even stalling protein synthesis entirely. Therefore, a well-functioning E site not only promotes efficiency but also maintains fidelity in translating genetic information into functional proteins.

Related terms

A site: The A site, or aminoacyl site, is the ribosomal binding site that holds the tRNA carrying the next amino acid to be added to the growing polypeptide chain.

P site: The P site, or peptidyl site, is the ribosomal binding site where the tRNA holding the growing polypeptide chain is located during translation.

Ribosome: A ribosome is a complex molecular machine found within all living cells that performs biological protein synthesis (translation).