The eukaryotic release factor is a key protein involved in the final stage of protein synthesis, known as termination, within eukaryotic cells. Its primary function is to signal the ribosome to stop building the polypeptide chain when it encounters a stop codon on the messenger RNA (mRNA).
Key Functions of the Eukaryotic Release Factor
During the process of translation, ribosomes read the genetic code carried by mRNA, adding amino acids one by one to form a polypeptide chain. This process continues until a specific signal, a stop codon (UAA, UAG, or UGA), appears in the ribosome's A site. Unlike regular codons, stop codons are not recognized by transfer RNAs (tRNAs) that carry amino acids.
Instead, the stop codon is recognized by the eukaryotic release factor. Based on the provided reference, the function involves:
- Binding to the Stop Codon: "It binds to the stop codon in the A site in place of a tRNA." This binding event is the crucial signal that triggers the termination phase of translation.
- Mediating Polypeptide Release: Upon binding to the stop codon, the release factor's presence in the A site induces a conformational change in the ribosome. This change activates the peptidyl transferase center to catalyze the hydrolysis of the ester bond linking the completed polypeptide chain to the tRNA located in the P site. This hydrolysis reaction liberates the newly synthesized protein from the ribosome.
The reference also includes the statement: "It releases the amino acid from its tRNA to allow the amino acid to be added to the growing polypeptide."
Why is this function important?
Accurate termination of translation is vital for cellular health and function.
- Ensuring Correct Protein Length: It prevents the ribosome from adding extra, incorrect amino acids past the stop codon.
- Maintaining Protein Structure and Function: Proteins of the wrong length can fold improperly or be non-functional.
- Preventing Ribosome Recycling Issues: Proper termination allows the ribosome to disassemble and be recycled for further rounds of translation.
Summary
In summary, the primary function of the eukaryotic release factor is to recognize stop codons in the ribosomal A site, which leads to the hydrolysis of the bond between the final tRNA and the completed polypeptide chain, thereby terminating translation and releasing the protein.
