Release factors

Definition

Release factors are proteins that play a crucial role in the termination of translation during protein synthesis. They recognize the stop codons on the mRNA sequence and facilitate the release of the newly synthesized polypeptide chain from the ribosome, effectively ending the process of translation. The action of release factors ensures that the protein is correctly released and can undergo further folding and post-translational modifications.

5 Must Know Facts For Your Next Test

1. There are two main types of release factors in prokaryotes: RF1, which recognizes UAA and UAG stop codons, and RF2, which recognizes UAA and UGA stop codons.
2. In eukaryotes, there is a single release factor, eRF1, which can recognize all three stop codons (UAA, UAG, UGA).
3. Upon binding to the ribosome, release factors trigger hydrolysis of the bond between the tRNA and the polypeptide chain, releasing the newly formed protein.
4. Release factors also play a role in recycling ribosomal subunits and tRNA after translation termination, helping to prepare them for subsequent rounds of translation.
5. Mutations affecting release factors can lead to improper termination of translation, potentially resulting in nonfunctional proteins or diseases.

Review Questions

• How do release factors function in recognizing stop codons during translation termination?
  • Release factors function by binding to specific stop codons on the mRNA during translation termination. These proteins have domains that mimic tRNA, allowing them to fit into the A site of the ribosome when a stop codon is present. Once bound, they trigger the hydrolysis of the bond between the polypeptide chain and its tRNA, leading to the release of the completed protein from the ribosome.
• Discuss the differences between prokaryotic and eukaryotic release factors in terms of their structure and function.
  • Prokaryotic release factors consist of two distinct proteins (RF1 and RF2), each specialized for recognizing specific stop codons. In contrast, eukaryotic cells use a single release factor (eRF1) that recognizes all three stop codons. The structural differences include additional domains in eRF1 that allow for broader recognition capability, while both types ultimately serve to terminate translation by facilitating peptide release from the ribosome.
• Evaluate how mutations in release factors can impact protein synthesis and cellular function.
  • Mutations in release factors can lead to misrecognition of stop codons, resulting in either premature termination or read-through of translation. This could produce truncated proteins or longer polypeptides that may be nonfunctional or toxic. Such errors in protein synthesis can disrupt cellular processes and contribute to various diseases, illustrating how critical accurate termination is for maintaining proper cellular function.

Related terms

codon: A codon is a sequence of three nucleotides on mRNA that corresponds to a specific amino acid or a stop signal during translation.

ribosome: A ribosome is a molecular machine found within all living cells that facilitates the translation of mRNA into proteins by assembling amino acids in the correct order.

peptidyl transferase: Peptidyl transferase is an enzymatic activity associated with ribosomes that catalyzes the formation of peptide bonds between amino acids during protein synthesis.