The polypeptide tunnel exit of the mitochondrial ribosome is tailored to meet the specific requirements of the organelle

Gruschke, Steffi; Ott, Martin

doi:10.1002/bies.201000081

Cited by 32 publications

(14 citation statements)

References 61 publications

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“…Consequently, all mito-ribosomes are permanently tethered to the inner membrane and its composition, especially around the polypeptide exit tunnel, is much different from bacterial ribosome. This peculiarity allows a better coordination of the synthesis of the highly hydrophobic mitochondrial proteins and their immediate assembly within the mitochondrial membrane [132]. The possibility exists that, beside the cytoplasmic ribosomes producing mainly soluble cellular proteins, a minor fraction of such specialized membrane-bound ribosomes also exists in Mollicutes , a cellular strategy that certainly allows better efficiency of certain membrane proteins.…”

Section: Resultsmentioning

confidence: 99%

Predicting the Minimal Translation Apparatus: Lessons from the Reductive Evolution of Mollicutes

et al. 2014

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Mollicutes is a class of parasitic bacteria that have evolved from a common Firmicutes ancestor mostly by massive genome reduction. With genomes under 1 Mbp in size, most Mollicutes species retain the capacity to replicate and grow autonomously. The major goal of this work was to identify the minimal set of proteins that can sustain ribosome biogenesis and translation of the genetic code in these bacteria. Using the experimentally validated genes from the model bacteria Escherichia coli and Bacillus subtilis as input, genes encoding proteins of the core translation machinery were predicted in 39 distinct Mollicutes species, 33 of which are culturable. The set of 260 input genes encodes proteins involved in ribosome biogenesis, tRNA maturation and aminoacylation, as well as proteins cofactors required for mRNA translation and RNA decay. A core set of 104 of these proteins is found in all species analyzed. Genes encoding proteins involved in post-translational modifications of ribosomal proteins and translation cofactors, post-transcriptional modifications of t+rRNA, in ribosome assembly and RNA degradation are the most frequently lost. As expected, genes coding for aminoacyl-tRNA synthetases, ribosomal proteins and initiation, elongation and termination factors are the most persistent (i.e. conserved in a majority of genomes). Enzymes introducing nucleotides modifications in the anticodon loop of tRNA, in helix 44 of 16S rRNA and in helices 69 and 80 of 23S rRNA, all essential for decoding and facilitating peptidyl transfer, are maintained in all species. Reconstruction of genome evolution in Mollicutes revealed that, beside many gene losses, occasional gains by horizontal gene transfer also occurred. This analysis not only showed that slightly different solutions for preserving a functional, albeit minimal, protein synthetizing machinery have emerged in these successive rounds of reductive evolution but also has broad implications in guiding the reconstruction of a minimal cell by synthetic biology approaches.

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Section: Resultsmentioning

confidence: 99%

Predicting the Minimal Translation Apparatus: Lessons from the Reductive Evolution of Mollicutes

et al. 2014

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“…In contrast to the situation with cytoplasmic ribosomes, where a variety of possible destinations for the synthesized nascent polypeptide chains are possible, all of the nascent chains synthesized by the mammalian mitoribosome are inserted into the mtIM, and it is most likely that these polypeptides are inserted co-translationally into mtIM [41, 42]. Therefore, detailed knowledge of the architecture and composition the polypeptide-exit tunnel in the mito-LSU has been of particular interest.…”

Section: Structure Of the Mammalian Mitoribosomementioning

confidence: 99%

The 55S mammalian mitochondrial ribosome and its tRNA-exit region

2015

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Mitochondria carry their own genetic material and gene-expression machinery, including ribosomes, which are responsible for synthesizing polypeptides that form essential components of the complexes involved in oxidative phosphorylation (or ATP generation) for the eukaryotic cell. Mitochondrial ribosomes (mitoribosomes) are quite divergent from cytoplasmic ribosomes in both composition and structure even as their main functional cores, such as the mRNA decoding and peptidyl transferase sites, are highly conserved. Remarkable progress has been made recently towards understanding the structure of mitoribosomes, by obtaining high-resolution cryo-electron microscopic (cryo-EM) maps. These studies confirm previous structural findings that had revealed that a significant reduction in size of ribosomal RNAs has caused topological changes in some of the functionally relevant regions, including the transfer RNA (tRNA)-binding sites and the nascent polypeptide-exit tunnel, within the structure of the mammalian mitoribosome. In addition, these studies provide unprecedented detailed views of the molecular architecture of those regions. In this review, we summarize the current state of knowledge of the structure of the mammalian mitoribosome and describe the molecular environment of its tRNA-exit region.

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“…Nuclear encoded proteins are imported into the mitochondria by translocases (5,31), while the mitochondrially encoded proteins are synthesized within the organelle by mitochondrial ribosomes and inserted into the inner membrane (2,32). In addition, eukaryotic cells have a quality control system monitoring their mitochondria (24,33).…”

Section: Discussionmentioning

confidence: 99%

A bifunctional protein regulates mitochondrial protein synthesis

Richman

Davies

Shearwood

et al. 2014

Nucleic Acids Research

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Mitochondrial gene expression is predominantly regulated at the post-transcriptional level and mitochondrial ribonucleic acid (RNA)-binding proteins play a key role in RNA metabolism and protein synthesis. The AU-binding homolog of enoyl-coenzyme A (CoA) hydratase (AUH) is a bifunctional protein with RNA-binding activity and a role in leucine catabolism. AUH has a mitochondrial targeting sequence, however, its role in mitochondrial function has not been investigated. Here, we found that AUH localizes to the inner mitochondrial membrane and matrix where it associates with mitochondrial ribosomes and regulates protein synthesis. Decrease or overexpression of the AUH protein in cells causes defects in mitochondrial translation that lead to changes in mitochondrial morphology, decreased mitochondrial RNA stability, biogenesis and respiratory function. Because of its role in leucine metabolism, we investigated the importance of the catalytic activity of AUH and found that it affects the regulation of mitochondrial translation and biogenesis in response to leucine.

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The polypeptide tunnel exit of the mitochondrial ribosome is tailored to meet the specific requirements of the organelle

Cited by 32 publications

References 61 publications

Predicting the Minimal Translation Apparatus: Lessons from the Reductive Evolution of Mollicutes

Predicting the Minimal Translation Apparatus: Lessons from the Reductive Evolution of Mollicutes

The 55S mammalian mitochondrial ribosome and its tRNA-exit region

A bifunctional protein regulates mitochondrial protein synthesis

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