Journal
NATURE COMMUNICATIONS
Volume 11, Issue 1, Pages -Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/s41467-020-17715-2
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Funding
- Simons Foundation [349247]
- NYSTAR
- NIH [R01 GM61576, GM103310]
- Agouron Institute [F00316]
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The mammalian mitochondrial ribosome (mitoribosome) and its associated translational factors have evolved to accommodate greater participation of proteins in mitochondrial translation. Here we present the 2.68-3.96 angstrom cryo-EM structures of the human 55S mitoribosome in complex with the human mitochondrial elongation factor G1 (EF-G1(mt)) in three distinct conformational states, including an intermediate state and a post-translocational state. These structures reveal the role of several mitochondria-specific (mito-specific) mitoribosomal proteins (MRPs) and a mito-specific segment of EF-G1(mt) in mitochondrial tRNA (tRNA(mt)) translocation. In particular, the mito-specific C-terminal extension in EF-G1(mt) is directly involved in translocation of the acceptor arm of the A-site tRNA(mt). In addition to the ratchet-like and independent head-swiveling motions exhibited by the small mitoribosomal subunit, we discover significant conformational changes in MRP mL45 at the nascent polypeptide-exit site within the large mitoribosomal subunit that could be critical for tethering of the elongating mitoribosome onto the inner-mitochondrial membrane. Translation within mitochondria is carried out by specialized mitoribosomes and translational factors. Here the authors describe cryo-EM structures of the human mitochondrial translation elongation factor G1 in complex with human mitoribosomes, revealing distinct mechanism that include conformational changes at the polypeptide exit tunnel.
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