What is the molecular basis of unlocking, which governs codon-anticodon movement during translocation?
After the amino acid is incorporated into the nascent peptide chain, the tRNAs (paired to mRNA) are translocated to their adjacent sites in the ribosome. This reaction is catalyzed by elongation factor G, which hydrolyzes GTP in the process. Kinetic studies indicate that GTP hydrolysis precedes a conformational change termed “unlocking” that limits the rate of codon-anticodon movement and phosphate release. While there are some compelling data to suggest that unlocking involves rotation of the 30S head domain, the molecular basis of unlocking remains largely unknown.
