Role of elongation factors EF-Tu and EF-G in prokaryotes?

• A. EF-Tu delivers aminoacyl-tRNA to the A site; EF-G mediates translocation.
• B. EF-Tu edits the tRNA; EF-G recruits ribosomal subunits.
• C. EF-Tu catalyzes peptide bond formation; EF-G caps at stop codon.
• D. EF-Tu removes ribosome from mRNA; EF-G loads mRNA.

Answer: (C)

During prokaryotic translation elongation, two elongation factors coordinate the movement of tRNA and mRNA through the ribosome. EF-Tu, bound to GTP, delivers the correct aminoacyl-tRNA to the ribosome A site and helps ensure proper codon–anticodon pairing; once the correct fit is established, GTP is hydrolyzed and EF-Tu-GDP dissociates, leaving the aminoacyl-tRNA in place for peptide bond formation. The bond itself is formed by the ribosome's peptidyl transferase center, not by EF-Tu. After the peptide bond forms, EF-G, another GTPase, binds and uses the energy of GTP hydrolysis to move the ribosome along the mRNA in a translocation step, shifting the tRNAs from the A site to the P site and from the P site to the E site to prepare for the next aminoacyl-tRNA entry. Termination at stop codons is handled by release factors, not by EF-G capping. In short, EF-Tu delivers aminoacyl-tRNA to the A site, and EF-G drives translocation after peptide bond formation.