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Article Abstract
Discrimination of tRNA on the ribosome occurs in two consecutive steps: initial selection and proofreading. Here we propose a proofreading mechanism based on comparison of crystal structures of the 70S ribosome with an empty A site or with the A site occupied by uncharged cognate or near-cognate tRNA. We observe that ribosomal proteins S13, S19, L16, L25, L27 and L31 are actively involved in the proofreading of tRNA. We suggest that proofreading begins with the monitoring of the entire anticodon loop of tRNA by nucleotides from 16S rRNA (helices 18 and 44) of the small subunit and 23S rRNA (helix 69) of the large subunit with involvement of magnesium ions. Subsequently, the elbow region is scanned by rRNA (helices 38 and 89) and proteins from the large subunit determining whether to accommodate the acceptor end of tRNA in the peptidyl transferase center or not.
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Article Synopsis
- The mammalian mitochondrial protein synthesis system is responsible for synthesizing 13 crucial subunits for energy production, but the exact role of IF-3mt in translation initiation is still unclear.
- Researchers created a mitochondrial translation system to explore IF-3mt's proofreading abilities, revealing it helps distinguish between different start codons for more accurate protein synthesis.
- The findings indicate that IF-3mt not only supports initiation from standard AUG start codons but can also facilitate initiation from non-AUG codons like AUA, highlighting its adaptability in working with leaderless mRNAs.