During translation, aminoacyl-tRNA is delivered to the ribosome A-site by which elongation factor, and what energy source drives this step?
- A eEF-2 in eukaryotes (EF-G in prokaryotes); GTP hydrolysis
- B eIF-5 in eukaryotes; ATP hydrolysis
- C eRF-1 in eukaryotes; GTP hydrolysis
- D eEF-1α in eukaryotes (EF-Tu in prokaryotes); GTP hydrolysis ✓
Explanation
In eukaryotes, aminoacyl-tRNA is escorted to the ribosomal A-site as a ternary complex with eEF-1α (homologous to prokaryotic EF-Tu) and GTP. Correct codon-anticodon recognition triggers GTP hydrolysis by eEF-1α, causing conformational change and release of eEF-1α·GDP; the aminoacyl-tRNA is accommodated into the A-site. eEF-2 (prokaryotic EF-G) is the translocase that uses GTP hydrolysis to translocate the ribosome 3 nucleotides (codon) along mRNA, moving peptidyl-tRNA from A- to P-site. Diphtheria toxin ADP-ribosylates a modified histidine (diphthamide) in eEF-2, blocking translocation. Fusidic acid blocks prokaryotic EF-G.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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