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- Title
Parallel Structural Evolution of Mitochondrial Ribosomes and OXPHOS Complexes.
- Authors
van der Sluis, Eli O.; Bauerschmitt, Heike; Becker, Thomas; Mielke, Thorsten; Frauenfeld, Jens; Berninghausen, Otto; Neupert, Walter; Herrmann, Johannes M.; Beckmann, Roland
- Abstract
The fivemacromolecular complexes that jointlymediate oxidative phosphorylation (OXPHOS) inmitochondria consist of many more subunits than those of bacteria, yet, it remains unclear bywhich evolutionary mechanism(s) these novel subunitswere recruited. Even less well understood is the structural evolution of mitochondrial ribosomes (mitoribosomes): while it was long thought that their exceptionally high protein content would physically compensate for their uniquely low amount of ribosomal RNA (rRNA), this hypothesis has been refuted by structural studies. Here, we present a cryo-electron microscopy structure of the 73S mitoribosome from Neurospora crassa, together with genomic and proteomic analyses of mitoribosomecomposition across the eukaryotic domain. Surprisingly, ourfindings reveal thatbothstructurallyandcompositionally, mitoribosomeshave evolved very similarly tomitochondrial OXPHOS complexes via two distinct phases: A constructive phase that mainly acted early in eukaryote evolution, resulting in the recruitment of altogether approximately 75 novel subunits, and a reductive phase that acted duringmetazoan evolution, resulting in gradual length-reduction of mitochondrially encoded rRNAs and OXPHOS proteins. Both phases can be well explained by the accumulation of (slightly) deleteriousmutations and deletions, respectively, in mitochondrially encoded rRNAs andOXPHOS proteins. We argue that the main role of the newly recruited (nuclear encoded) ribosomal- and OXPHOS proteins is to provide structural compensation to the mutationally destabilized mitochondrially encoded components. While the newly recruited proteins probably provide a selective advantageowingto their compensatorynature, andwhile theirpresencemay have openedevolutionarypathways toward novel mitochondrion-specific functions, we emphasize that the initial events that resulted in their recruitment was nonadaptive in nature. Our framework is supported by population genetic studies, and it can explain the complete structural evolution of mitochondrial ribosomes and OXPHOS complexes, as well as many observed functions of individual proteins.
- Subjects
RIBOSOMAL DNA; NUCLEOPROTEINS; PROTOPLASM; PROTEINS; BIOLOGICAL evolution
- Publication
Genome Biology & Evolution, 2015, Vol 7, Issue 5, p1235
- ISSN
1759-6653
- Publication type
Article
- DOI
10.1093/gbe/evv061