key term - Release Factors

Definition

Release factors are proteins that play a crucial role in the termination phase of translation by recognizing stop codons in the mRNA sequence and promoting the release of the newly synthesized polypeptide chain from the ribosome. These factors ensure that protein synthesis is completed accurately and efficiently, preventing errors that could lead to nonfunctional proteins. They work by facilitating the hydrolysis of the bond between the polypeptide and the tRNA, allowing the protein to be released into the cellular environment.

5 Must Know Facts For Your Next Test

1. There are two main types of release factors: Class I release factors recognize stop codons and bind to the A site of the ribosome, while Class II release factors help to displace Class I release factors after they have acted.
2. In bacteria, the primary release factor is RF1 or RF2, while eukaryotes utilize eRF1 to recognize all three stop codons.
3. Release factors are essential for ensuring that translation does not continue beyond the intended protein coding sequence, preventing the production of truncated proteins.
4. The binding of release factors induces conformational changes in the ribosome that promote peptidyl-tRNA hydrolysis, leading to polypeptide release.
5. After polypeptide release, the ribosome must dissociate from mRNA and tRNA to prepare for another round of translation, a process also influenced by release factors.

Review Questions

• How do release factors contribute to the accuracy of protein synthesis during translation termination?
  • Release factors enhance the accuracy of protein synthesis by specifically recognizing stop codons in the mRNA sequence. When a stop codon is encountered at the ribosome's A site, release factors bind to it and facilitate the hydrolysis of the bond between the polypeptide and tRNA. This process ensures that translation stops at precisely the right moment, preventing errors that could result from extending protein synthesis beyond the intended coding region.
• Discuss the differences between bacterial and eukaryotic release factors in terms of their structure and function.
  • Bacterial release factors include RF1 and RF2, which each recognize specific stop codons, while eukaryotes use eRF1 to recognize all three stop codons. Structurally, eRF1 is more complex than bacterial factors and can interact with additional proteins for effective termination. These differences reflect variations in translation machinery between prokaryotes and eukaryotes, with eukaryotic systems often being more intricate due to their cellular organization.
• Evaluate the role of release factors in maintaining cellular homeostasis through their function in protein synthesis.
  • Release factors play a critical role in maintaining cellular homeostasis by ensuring that proteins are synthesized correctly and efficiently. By terminating translation at precise locations dictated by stop codons, they prevent the production of defective or incomplete proteins that could disrupt cellular function. Any failure in this mechanism could lead to malfunctioning proteins accumulating within cells, potentially causing cellular stress or disease states. Thus, their role in accurate protein synthesis is essential for overall cellular health and function.

Related terms

Stop Codons: Specific codons in mRNA, such as UAA, UAG, and UGA, that signal the termination of protein synthesis.

Ribosome: A molecular machine composed of ribosomal RNA and proteins that facilitates the translation of mRNA into a polypeptide chain.

Polypeptide Chain:

A long chain of amino acids linked by peptide bonds, which folds into a functional protein after synthesis.