key term - Peptidyl transferase activity

Definition

Peptidyl transferase activity refers to the enzymatic function that catalyzes the formation of peptide bonds between amino acids during protein synthesis. This activity is a crucial function of the ribosome, where it facilitates the elongation of the polypeptide chain by transferring the growing peptide from the P site to the A site, ensuring that proteins are assembled correctly from their constituent amino acids.

5 Must Know Facts For Your Next Test

1. Peptidyl transferase activity is primarily associated with the large subunit of the ribosome, specifically in the 50S subunit in prokaryotes and the 60S subunit in eukaryotes.
2. This activity is catalyzed by ribosomal RNA rather than protein, demonstrating that rRNA can function as a ribozyme.
3. The formation of peptide bonds through peptidyl transferase activity occurs during the elongation phase of translation, linking amino acids together to form a polypeptide chain.
4. Peptidyl transferase activity requires the presence of GTP and elongation factors to ensure accurate and efficient protein synthesis.
5. Mutations or dysfunctions in peptidyl transferase activity can lead to defective protein synthesis, which may result in various diseases or cellular malfunctions.

Review Questions

• How does peptidyl transferase activity contribute to the process of translation?
  • Peptidyl transferase activity is essential for translation as it catalyzes the formation of peptide bonds between amino acids during protein synthesis. This activity takes place within the ribosome, specifically at the large subunit, where it facilitates the transfer of the growing polypeptide chain from one tRNA in the P site to another tRNA in the A site. Without this enzymatic function, the assembly of proteins from their amino acid building blocks would be impossible.
• Discuss the role of ribosomal RNA in peptidyl transferase activity and how it differs from conventional enzymes.
  • Ribosomal RNA plays a pivotal role in peptidyl transferase activity by acting as a catalyst for peptide bond formation during translation. Unlike conventional enzymes that are typically composed of proteins, rRNA functions as a ribozyme—an RNA molecule with enzymatic capabilities. This highlights a unique aspect of molecular biology, where RNA can perform critical catalytic functions within the ribosome, underscoring the evolutionary significance and versatility of RNA.
• Evaluate the implications of impaired peptidyl transferase activity on cellular function and overall health.
  • Impaired peptidyl transferase activity can have serious implications for cellular function and overall health. When this activity is disrupted, protein synthesis becomes inefficient or incorrect, potentially leading to truncated or misfolded proteins. Such abnormalities can cause cellular stress responses and may contribute to various diseases, including neurodegenerative disorders and cancers. Understanding these implications helps illuminate the importance of ribosomal functions and their impact on cellular homeostasis and organismal health.

Related terms

Ribosomal RNA (rRNA): The type of RNA that, along with proteins, makes up the ribosome and plays a key role in catalyzing peptide bond formation.

Aminoacyl-tRNA: A molecule formed when an amino acid is attached to its corresponding transfer RNA (tRNA), allowing for the specific incorporation of amino acids into a growing polypeptide chain.

Translation:

The process by which ribosomes synthesize proteins by decoding messenger RNA (mRNA) into a sequence of amino acids.