Clingy genes: Why were genes for ribosomal proteins retained in many mitochondrial genomes?

Why mitochondria still retain their own genome is a puzzle given the enormous effort to maintain a mitochondrial translation machinery. Most mitochondrially encoded proteins are membrane-embedded subunits of the respiratory chain. Their hydrophobicity presumably impedes their import into mitochondri...

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Bibliographic Details
Published in:Biochimica et biophysica acta. Bioenergetics 2020-11, Vol.1861 (11), p.148275-148275, Article 148275
Main Authors: Bertgen, Lea, Mühlhaus, Timo, Herrmann, Johannes M.
Format: Article
Language:English
Subjects:
Eukaryota - genetics
Eukaryota - metabolism
Eukaryotes
Evolution
Gene transfer
Genome, Mitochondrial
Mitochondria
Mitochondrial Proteins - genetics
Mitochondrial Proteins - metabolism
Protein Biosynthesis
Respiratory chain
Ribosomal Proteins - genetics
Ribosomal Proteins - metabolism
Ribosomes
Ribosomes - genetics
Ribosomes - metabolism
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Summary:Why mitochondria still retain their own genome is a puzzle given the enormous effort to maintain a mitochondrial translation machinery. Most mitochondrially encoded proteins are membrane-embedded subunits of the respiratory chain. Their hydrophobicity presumably impedes their import into mitochondria. However, many mitochondrial genomes also encode protein subunits of the mitochondrial ribosome. These proteins lack transmembrane domains and hydrophobicity cannot explain why their genes remained in mitochondria. In this review, we provide an overview about mitochondrially encoded subunits of mitochondrial ribosomes of fungi, plants and protists. Moreover, we discuss and evaluate different hypotheses which were put forward to explain why (ribosomal) proteins remained mitochondrially encoded. It seems likely that the synthesis of ribosomal proteins in the mitochondrial matrix is used to regulate the assembly of the mitochondrial ribosome within mitochondria and to avoid problems that mitochondrial proteins might pose for cytosolic proteostasis and for the assembly of cytosolic ribosomes. •Mitochondrial genomes code for a very small number of proteins•Membrane proteins and, often, ribosomal proteins are mitochondrially encoded.•Cytosolic expression of these proteins can hazard cellular proteostasis.•Protein expression in mitochondria allows local regulation.•Gene transfer to the nucleus comes at a ‘protein-specific prize’.
ISSN:0005-2728
1879-2650
DOI:10.1016/j.bbabio.2020.148275