Cryo-EM structure of the small subunit of the mammalian mitochondrial ribosome

Abstract

The authors wish to note, "The availability of the high-resolution structures of the complete 55 S mitoribosome recently published in Amunts et al. (1) and Greber et al. (2) have shown that our cryo-EM map is consistent with their high-resolution coordinates. However, a comparison with these two studies shows that at our resolution of 7 Å, some of our placements, particularly of the mito-specific MRPs, were in error. While this comparison highlights the difficulty of interpretation of multiple nonhomologous MRPs at our modest resolution, it also shows that the fold of the nucleic acid component of the RNP complex, the 12S rRNA, could be traced. We will be updating our previously published coordinates in light of the new papers." www.pnas.org/cgi

Mitochondrial ribosome assembly in health and disease

“…In S. cerevisiae mitochondria, 26 of the 38 mtSSU proteins and 30 of the 46 mtLSU proteins are homologous to E. coli proteins, while the rest are specific to mitoribosomes [6,14]. In mammals, 16 of the 30 mtSSU proteins and 28 of the 50 mtLSU proteins are homologs of proteins present in E. coli while the rest are mitospecific proteins [5,11,12,15,16]. As a consequence, yeast 74S and particularly human 55S mitoribosomes differ from bacterial (70S) and cytoplasmic ribosomes (80S) in their lower RNA:protein ratio, where significant amounts of RNA have been replaced by mitochondrion-specific proteins.…”

“…Recent developments in electron microscopy have allowed resolving the structure of yeast mtLSU [13] and both mammalian mtLSU [11,12,15] and mtSSU [16,17] at near-atomic resolution, which will be summarized in depth in this review. These structures have provided a wealth of novel information, raising the next obvious question as to how these ribonucleoprotein macromachines are assembled.…”

“…The Ban group focused mainly on the mammalian mtLSU, where the porcine mtLSU (Sus scrofa) was resolved at both 4.9Å and 3.4Å resolution [11,15]. Contributing to the era of mitochondrial structural revolution, Agrawal's group resolved the cryo-EM structure of the mammalian mtSSU at 7Å resolution [16]. To finalize the impressive race between the Ramakrishnan and Ban groups, during the preparation of this manuscript, they have resolved at 3.5Å or 3.8Å resolution the complete structures of the 55S human [25] or porcine [26] mitoribosomes, respectively.…”

“…Overall, the high-resolution reconstructions have provided a wealth of novel information, specifically noting the similarities and differences between yeast and mammalian mitoribosomes ( Fig. 1) [4,5,13,15,16,25,26].…”

Organization of the mitochondrial translation machinery studied in situ by cryoelectron tomography

“…Only very recently, high-resolution structures for the large subunit of the mammalian and yeast mitoribosome 9,10 and the small subunit of the mammalian mitoribosome 11 were published. Since the mitoribosomes used in these single particle cryoelectron microscopy (cryo-EM) experiments were recovered from salt-washed detergent extracts, membrane-binding sites remained hypothetical.…”