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bioRxiv · 10.1101/2020.12.20.423689

Structures of the human mitochondrial ribosome recycling complexes reveal distinct mechanisms of recycling and antibiotic resistance

Koripella, R. K.·Deep, A.·Agrawal, E. K.·Keshavan, P.·Banavali, N. K.·Agrawal, R. K.
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Abstract

Ribosomes are recycled for a new round of translation initiation by dissociation of ribosomal subunits, messenger RNA and transfer RNA from their translational post-termination complex. Mitochondrial ribosome recycling factor (RRFmt) and a recycling-specific homolog of elongation factor G (EF-G2mt) are two proteins with mitochondria-specific additional sequences that catalyze the recycling step in human mitochondria. We have determined high-resolution cryo-EM structures of the human 55S mitochondrial ribosome (mitoribosome) in complex with RRFmt, and the mitoribosomal large 39S subunit in complex with both RRFmt and EF-G2mt. In addition, we have captured the structure of a short-lived intermediate state of the 55S*RRFmt*EF-G2mt complex. These structures clarify the role of a mitochondria-specific segment of RRFmt in mitoribosome recycling, identify the structural distinctions between the two isoforms of EF-Gmt that confer their functional specificity, capture recycling-specific conformational changes in the L7/L12 stalk-base region, and suggest a distinct mechanistic sequence of events in mitoribosome recycling. Furthermore, biochemical and structural assessments of the sensitivity of EF-G2mt to the antibiotic fusidic acid reveals that the molecular mechanism of antibiotic resistance for EF-G2mt is markedly different from that exhibited by mitochondrial elongation factor EF-G1mt, suggesting that these two homologous mitochondrial proteins have evolved diversely to negate the effect of a bacterial antibiotics.

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Koripella, R. K., Deep, A., Agrawal, E. K., Keshavan, P., Banavali, N. K., Agrawal, R. K.. 2020-12-21. Structures of the human mitochondrial ribosome recycling complexes reveal distinct mechanisms of recycling and antibiotic resistance. https://doi.org/10.1101/2020.12.20.423689

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