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Structures of the human mitochondrial ribosome bound to EF-G1 reveal distinct features of mitochondrial translation elongation.

Nature communications (2020-08-02)
Ravi Kiran Koripella, Manjuli R Sharma, Kalpana Bhargava, Partha P Datta, Prem S Kaushal, Pooja Keshavan, Linda L Spremulli, Nilesh K Banavali, Rajendra K Agrawal
RESUMEN

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 Å cryo-EM structures of the human 55S mitoribosome in complex with the human mitochondrial elongation factor G1 (EF-G1mt) 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-G1mt in mitochondrial tRNA (tRNAmt) translocation. In particular, the mito-specific C-terminal extension in EF-G1mt is directly involved in translocation of the acceptor arm of the A-site tRNAmt. 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.

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β,γ-Methyleneguanosine 5′-triphosphate sodium salt, ≥98% (HPLC)