During the elongation stage of eukaryotic protein synthesis:...

During the elongation stage of eukaryotic protein synthesis: A. the incoming aminoacyl-tRNA binds to the P site. B. a new peptide bond is synthesized by peptidyl transferase site of the large ribosomal subunit in a GTP-requiring reaction. C. the peptide, still bound to a tRNA molecule, is transloated to a different site on the ribosome. D. streptomycin can cause premature release of the incomplete peptide. E. peptide bond formation occurs by the attack of the carboxyl group of the incoming aminoacyl-tRNA on the amino group of the growing peptide chain.

During the elongation stage of eukaryotic protein synthesis:
A. the incoming aminoacyl-tRNA binds to the P site.
B. a new peptide bond is synthesized by peptidyl transferase site of the large ribosomal subunit in a GTP-requiring reaction.
C. the peptide, still bound to a tRNA molecule, is transloated to a different site on the ribosome.
D. streptomycin can cause premature release of the incomplete peptide.
E. peptide bond formation occurs by the attack of the carboxyl group of the incoming aminoacyl-tRNA on the amino group of the growing peptide chain.

Key Concepts

Protein Synthesis Elongation Stage

This is the phase of translation where amino acids are sequentially added to a growing polypeptide chain. It includes tRNA binding, peptide bond formation, and subsequent movement of the ribosome along the mRNA, ensuring that protein synthesis proceeds in a stepwise and regulated manner.

Ribosomal Binding Sites and tRNA Positioning

The ribosome has three key tRNA binding sites known as the A (aminoacyl), P (peptidyl), and E (exit) sites. During elongation, the incoming aminoacyl-tRNA first binds to the A site, the growing peptide chain is held at the P site, and after peptide bond formation, tRNAs move to different sites, facilitating accurate translation and efficient turnover.

Peptidyl Transferase Activity

Located within the large ribosomal subunit, peptidyl transferase is the enzymatic activity that catalyzes the formation of peptide bonds between amino acids. This reaction involves the nucleophilic attack of the amino group of the aminoacyl-tRNA (typically located at the A site) on the ester linkage of the peptidyl-tRNA (in the P site), thereby extending the polypeptide chain.

Translocation Mechanism

Translocation is the process by which the ribosome moves one codon along the mRNA following peptide bond formation. This movement shifts the positions of tRNAs from the A site to the P site and from the P site to the E site, a step that is essential for the ribosome to read the next codon and for ensuring that translation proceeds in the correct reading frame.

GTP-Dependent Elongation Factors

Elongation factors that require GTP binding and hydrolysis are critical in driving conformational changes during elongation. They facilitate correct tRNA positioning at the ribosome, promote translocation, and ensure overall fidelity and efficiency of the translation process.

Antibiotic Interference in Protein Synthesis

Certain antibiotics can disrupt protein synthesis by targeting the ribosome and interfering with key steps such as tRNA binding, peptide bond formation, or translocation. Although many such antibiotics are specific to prokaryotic ribosomes, understanding their mechanism provides insights into how translation can be prematurely terminated or otherwise hindered.

Please give Ace some feedback