Peptidyl transferase

Definition

Peptidyl transferase is an enzyme that catalyzes the formation of peptide bonds between amino acids during protein synthesis in ribosomes. This essential function occurs during translation, where the enzyme links the growing polypeptide chain to the incoming amino acid at the A site of the ribosome, thus facilitating protein assembly.

5 Must Know Facts For Your Next Test

1. Peptidyl transferase is part of the large subunit of the ribosome and is crucial for the elongation phase of translation.
2. It works by catalyzing the nucleophilic attack of the amino group of the incoming amino acid on the carbonyl carbon of the terminal amino acid in the growing polypeptide chain.
3. This reaction results in a peptide bond formation, which releases a molecule of water in a condensation reaction.
4. Peptidyl transferase does not have a separate catalytic protein; instead, its activity is attributed to ribosomal RNA (rRNA), making it a ribozyme.
5. Inhibitors of peptidyl transferase can disrupt protein synthesis and are used in various antibiotics to target bacterial translation.

Review Questions

• How does peptidyl transferase function within the ribosome during protein synthesis?
  • Peptidyl transferase functions as a catalyst for peptide bond formation between amino acids during translation. It operates in the ribosome's large subunit, specifically at the interface where the A and P sites are located. When an amino acid arrives at the A site, peptidyl transferase facilitates a nucleophilic attack that links it to the growing polypeptide chain at the P site, thus elongating the protein.
• Discuss the significance of peptidyl transferase being classified as a ribozyme rather than a traditional enzyme.
  • The classification of peptidyl transferase as a ribozyme highlights its unique nature, as it showcases how ribosomal RNA (rRNA) can exhibit catalytic properties without being a conventional protein enzyme. This emphasizes the central role of RNA in biological processes and challenges earlier notions that only proteins could function as enzymes. Understanding this distinction also provides insight into evolutionary biology and how early life forms may have relied on RNA for key biochemical functions.
• Evaluate the impact of inhibiting peptidyl transferase on bacterial translation and its implications for antibiotic development.
  • Inhibiting peptidyl transferase significantly disrupts bacterial translation, leading to halted protein synthesis and ultimately cell death. This mechanism forms the basis for several antibiotics that target this enzyme specifically, showcasing how understanding ribosomal function can inform drug design. Such inhibitors not only provide effective treatments for bacterial infections but also illustrate critical evolutionary differences between prokaryotic and eukaryotic translation machinery, which can be exploited to minimize side effects in human cells.

Related terms

Ribosome: A molecular machine composed of ribosomal RNA and proteins, responsible for synthesizing proteins by translating messenger RNA (mRNA) into polypeptide chains.

Amino Acid: The building blocks of proteins, each with a specific side chain that determines its properties and role in the polypeptide structure.

Translation: The process by which ribosomes synthesize proteins by decoding the information in messenger RNA (mRNA) and linking together the appropriate amino acids.