Fig. 7: Quality control mechanism in the early translation elongation by pep-tRNA drop-off.
From: Quality control of protein synthesis in the early elongation stage
In many bacteria, low codon optimality at the beginning of ORFs reduces the fidelity of translation and leads to produce a large amount of erroneous pep-tRNAs. However, the miscoded ribosome is efficiently disassembled by the concerted action of RF3 and RRF/EF-G (pep-tRNA drop-off), maintaining the accuracy of overall translation. In the middle and late region of mRNAs, translation smoothly proceeds due to high codon optimality to make a functional protein. If translation accuracy is compromised under some stress conditions in which codon optimality is disrupted, such as amino-acid starvation, RF2 senses the miscoding state and triggers release of the peptide of the pep-tRNA on the ribosome, followed by ribosome disassembly mediated by RF3, RRF, and EF-G via the same mechanism as ribosome recycling.
