Termination of translation

Definition

Termination of translation is the final step in the protein synthesis process where the ribosome releases the newly synthesized polypeptide chain upon reaching a stop codon on the mRNA. This process is crucial for ensuring that proteins are produced accurately and efficiently, allowing cells to function properly. Understanding this step helps to highlight the importance of ribosome structure and function in translating genetic information into functional proteins.

5 Must Know Facts For Your Next Test

1. Termination occurs when the ribosome encounters one of three stop codons: UAA, UAG, or UGA on the mRNA sequence.
2. Release factors bind to the ribosome at the A site upon recognizing a stop codon, triggering a series of events that lead to the release of the polypeptide.
3. During termination, water molecules are introduced into the peptidyl transferase center of the ribosome, facilitating hydrolysis of the bond between the polypeptide and tRNA.
4. The process of termination ensures that translation does not continue indefinitely, which could result in non-functional or truncated proteins.
5. After termination, the ribosomal subunits dissociate from each other and from the mRNA, allowing them to be reused in subsequent rounds of translation.

Review Questions

• What role do stop codons play in the termination of translation and how do they interact with ribosomal components?
  • Stop codons play a critical role in terminating translation by signaling to the ribosome that it should halt protein synthesis. When a stop codon is reached in the mRNA sequence, release factors bind to the ribosome at the A site. This interaction prompts a series of molecular changes that lead to the release of the newly synthesized polypeptide chain and disassembly of the ribosomal complex.
• Discuss how release factors facilitate the termination process and what mechanisms are involved in releasing the polypeptide chain.
  • Release factors facilitate termination by recognizing stop codons within the mRNA and binding to them. This binding prompts hydrolysis, where water molecules are used to cleave the bond between the polypeptide chain and tRNA. This action effectively releases the completed protein from the ribosome, allowing it to fold into its functional form and preventing any further addition of amino acids.
• Evaluate how mutations in stop codons could affect protein synthesis and overall cellular function.
  • Mutations in stop codons can lead to significant consequences for protein synthesis and cellular function. If a stop codon is mutated to encode an amino acid instead, it can result in a longer polypeptide than intended, potentially producing a non-functional or toxic protein. This misregulation could disrupt cellular processes and lead to diseases, illustrating how critical accurate termination is for maintaining proper cellular functions.

Related terms

stop codon:

A specific nucleotide triplet within mRNA that signals the end of translation, indicating that the ribosome should release the completed polypeptide.

release factors: Proteins that recognize stop codons during termination and facilitate the disassembly of the ribosomal complex, leading to the release of the newly formed protein.

polypeptide: A chain of amino acids linked by peptide bonds, which folds into a functional protein once synthesis is complete.