E site

Definition

The e site, or exit site, is one of the three binding sites on a ribosome during the process of translation, specifically for tRNA molecules. It is located at the ribosome's large subunit and plays a crucial role in the release of deacylated tRNA after it has contributed its amino acid to the growing polypeptide chain. Understanding the function of the e site is essential for grasping how ribosomes facilitate protein synthesis and manage the flow of tRNA during translation.

5 Must Know Facts For Your Next Test

1. The e site is critical for ensuring that tRNA molecules are released after they have donated their amino acids to the growing polypeptide chain.
2. After the peptide bond is formed between amino acids in the P site, the deacylated tRNA moves to the e site before being ejected from the ribosome.
3. The correct functioning of the e site is essential for maintaining translation efficiency and accuracy during protein synthesis.
4. Disruption or malfunctioning of the e site can lead to errors in protein synthesis, potentially resulting in nonfunctional proteins.
5. The dynamics of tRNA movement between the A, P, and e sites are key to understanding the overall mechanism of how ribosomes translate mRNA into proteins.

Review Questions

• How does the e site contribute to the overall process of translation?
  • The e site is integral to translation as it serves as the exit point for deacylated tRNA after it has delivered its amino acid to the growing polypeptide chain. After peptide bond formation occurs in the P site, the tRNA moves into the e site, where it is released from the ribosome. This process ensures that new tRNA can enter through the A site, allowing for continuous elongation of the polypeptide chain during protein synthesis.
• Compare and contrast the roles of the A, P, and e sites in a ribosome during translation.
  • The A, P, and e sites each play distinct but interrelated roles in translation. The A site is where aminoacyl-tRNA enters with a new amino acid, ready to be added to the growing chain. The P site holds the tRNA attached to the polypeptide chain during elongation. Finally, the e site is where deacylated tRNA exits after contributing its amino acid. Together, these sites facilitate a smooth transition of tRNA molecules and maintain efficient protein synthesis.
• Evaluate how mutations affecting the function of the e site could impact cellular function and organismal health.
  • Mutations that impair the function of the e site could severely disrupt protein synthesis by preventing proper release of deacylated tRNA. This could lead to accumulation of nonfunctional or incorrectly synthesized proteins, affecting vital cellular processes such as metabolism, signaling, and cell division. Such disruptions can manifest as diseases or developmental issues in an organism, highlighting the critical importance of ribosomal functionality for overall health.

Related terms

A site: The aminoacyl site, where new tRNA carrying an amino acid binds to the ribosome during protein synthesis.

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

Ribosome: A molecular machine made of ribosomal RNA and proteins that synthesizes proteins by translating messenger RNA.