During eukaryotic translation, the aminoacyl-tRNA that decodes a particular codon is recognized by the ribosome via codon-anticodon base pairing at the A site. After peptide bond formation, translocation moves the ribosome by one codon. Which GTPase is required for the translocation step in eukaryotes?
- A eIF-2 (alpha subunit)
- B eRF-3
- C eEF-2 (eukaryotic elongation factor 2) ✓
- D eIF-5B
Correct answer: C. eEF-2 (eukaryotic elongation factor 2)
Explanation
eEF-2 (eukaryotic elongation factor 2) is the translocase GTPase that catalyzes the movement of the ribosome along mRNA by exactly one codon after peptide bond formation, shifting peptidyl-tRNA from the A site to the P site. Diphtheria toxin and Pseudomonas exotoxin A inactivate eEF-2 by ADP-ribosylating a unique modified histidine residue called diphthamide, blocking translocation and halting protein synthesis. eIF-2 is required for initiator tRNA delivery to the 40S ribosome during initiation, not elongation.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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