Abstract
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.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Amino Acid Sequence
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Binding Sites
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Cryoelectron Microscopy
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HEK293 Cells
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Humans
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Mitochondria / metabolism*
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Mitochondria / ultrastructure
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Mitochondrial Membranes / metabolism
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Mitochondrial Membranes / ultrastructure
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Mitochondrial Proteins / chemistry*
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Mitochondrial Proteins / genetics
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Mitochondrial Proteins / metabolism
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Models, Molecular
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Nucleic Acid Conformation
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Peptide Chain Elongation, Translational*
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Peptide Elongation Factor G / chemistry*
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Peptide Elongation Factor G / genetics
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Peptide Elongation Factor G / metabolism
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Protein Binding
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Protein Conformation, alpha-Helical
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Protein Conformation, beta-Strand
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Protein Interaction Domains and Motifs
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RNA, Mitochondrial / chemistry*
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RNA, Mitochondrial / genetics
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RNA, Mitochondrial / metabolism
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RNA, Transfer / chemistry*
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RNA, Transfer / genetics
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RNA, Transfer / metabolism
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Ribosomal Proteins / chemistry*
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Ribosomal Proteins / genetics
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Ribosomal Proteins / metabolism
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Ribosomes / metabolism*
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Ribosomes / ultrastructure
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Sequence Alignment
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Sequence Homology, Amino Acid
Substances
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GFM1 protein, human
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Mitochondrial Proteins
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Peptide Elongation Factor G
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RNA, Mitochondrial
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Recombinant Proteins
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Ribosomal Proteins
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RNA, Transfer