Research Article

Structure of the large ribosomal subunit from human mitochondria

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Science  07 Nov 2014:
Vol. 346, Issue 6210, pp. 718-722
DOI: 10.1126/science.1258026

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Making mitochondrial hydrophobic proteins

Mitochondria produce chemical energy for the cell. Human mitochondria have their own specific ribosomes—mitoribosomes, which are distinct from cytoplasmic ribosomes. Mitoribosomes synthesize the mitochondrial membrane proteins that generate the chemical energy. Brown et al. used cryo–electron microscopy to determine the high-resolution structure of the large subunit of the human mitoribosome. The mitoribosome has a number of unique features, including an exit tunnel lined with hydrophobic amino acid residues.

Science, this issue p. 718

Abstract

Human mitochondrial ribosomes are highly divergent from all other known ribosomes and are specialized to exclusively translate membrane proteins. They are linked with hereditary mitochondrial diseases and are often the unintended targets of various clinically useful antibiotics. Using single-particle cryogenic electron microscopy, we have determined the structure of its large subunit to 3.4 angstrom resolution, revealing 48 proteins, 21 of which are specific to mitochondria. The structure unveils an adaptation of the exit tunnel for hydrophobic nascent peptides, extensive remodeling of the central protuberance, including recruitment of mitochondrial valine transfer RNA (tRNAVal) to play an integral structural role, and changes in the tRNA binding sites related to the unusual characteristics of mitochondrial tRNAs.

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