Mitochondrial ribosome

A ribosome in the mitochondria of eukaryotic cells

mitochondrion ribosome Is present in Eukaryotic cell A ribosome in mitochondria, responsible for completing the Organelle In translate Process. Mitochondrial ribosomal Settlement coefficient Between 55S-56S, it is the ribosome with the smallest sedimentation coefficient. Mitochondrial ribosomes of different organisms Physics chemical property Average ratio of differences in cytoplasm The size of the ribosome.

Chinese name: Mitochondrial ribosome
Foreign name: mitoribosome

Exists in: Eukaryotic cell
Responsible: translate process
Settlement coefficient: Between 55S-56S

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Development history

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Before the discovery of mitochondrial ribosomes, researchers had Eukaryotic cell Cytoplasmic neutralization Prokaryotic cell 80S ribosome and 70S ribosome 。

In 1967, O'Brien and Kalf et al Rat Hepatocyte mitochondrion Ribosomes are found in.^[1-2] When ribosomes first move from Organelle At the time of separation, researchers thought that these ribosomes were from prokaryote 70S ribosomes in ancestral cells.

In 1981, the mitochondrial ribosome rDNA The sequencing results of (human) were published, and the sequencing work was carried out in the cytoplasm ribosome rRNA Complete before the end of sequencing.^[3]

size

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Although the sedimentation coefficient ratio of mitochondrial ribosomes 70S ribosome The mitochondrial ribosomes are not degenerated 70S ribosomes or so-called "subribosomal particles". In fact, the mass and volume of mitochondrial ribosomes are larger than those of 70S ribosomes.^[4]

The small sedimentation coefficient of mitochondrial ribosomes is largely due to its protein content Higher and RNA The molecules are small.^[5]

form

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The general mitochondrial ribosome consists of 28S Ribosomal subunit （ Small subunit ）And 39S ribosomal subunits（ Large subunit ）Composition. Among these ribosomes, rRNA accounts for about 25%, Ribosomal protein (RP for short) accounts for about 75%. Mitochondrial ribosomes are the ribosomes with the highest protein content found.^[6]

Mitochondrial ribosomes contain 2-3 kinds of rRNAs and 85 kinds of RP.^[7] Other studies suggest that human mitochondrial ribosomes only contain 78 kinds of RP.^[8] Mitochondrial ribosome protein (referred to as "MRP" for short) can be divided into primary ones according to the order in which they bind to rRNA in the process of ribosome self-assembly Binding protein , secondary binding proteins, etc. In mitochondrial ribosome 39S Subunit L7, L13, L14, L21, L26 and L44 have been confirmed as primary binding proteins, while L8, L11, L28, L35, L40, L49 and L50 have been confirmed as secondary binding proteins.^[9] The 28S subunit of the mitochondrial ribosome contains about 950 nt of 12S MT-RNR1, while the 39S subunit contains about 1560 nt of 16S MT-RNR2. higher plant There is another kind of 5S rRNA with sedimentation coefficient in mitochondria, but it is different from the 5S rRNA of this rRNA cytoplasmic ribosome.

Genes and expression

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The components of mitochondrial ribosomes belong to nucleus And cytoplasm genome Therefore, mitochondrial ribosomes need to be co expressed by two genomes to form. Mammalian cell The genes encoding the components of mitochondrial ribosomes in the nucleus are evolving faster than those encoding 80S ribosomes.^[10-11]

All of the Ribosomal protein All by Nuclear gene And synthesized by 80S ribosome.^[12] These ribosomal proteins need to be Cytoplasmic matrix To complete the assembly of mitochondrial ribosomes.

Antibiotic resistance

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Although compared with 80S ribosome, mammal Mitochondrial ribosome and prokaryotic 70S ribosome More similar, they can still Protein Biosynthesis Inhibitors are distinguished by their sensitivity to antibiotics.^[13] However, some antibiotics not only inhibit 70S ribosome, but also inhibit mitochondrial ribosome. Therefore, some therapeutic bacteria pathogen Antibiotics of infection caused by invasion have certain side effects on patients (such as using chloramphenicol May cause Aplastic anemia , while using Aminoglycoside antibiotics Has Ototoxicity Etc.).^[14]

GTP affinity

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Mitochondrial ribosomes contain Guanosine triphosphate (GTP for short) GTP with strong affinity binding site 。 The GTP affinity of bovine mitochondrial ribosomal 28S subunit was Kd=17 ± 5.8 nM, while that of 39S subunit was Kd=15.3 ± 2.8 nM.^[15] At this height Affinity It is not available in 70S ribosomes and 80S ribosomes. It has been found that one of the GTP binding sites of bovine mitochondrial ribosomes is on the S5 protein of the 28S subunit. S5 is a unique RP of mitochondrial ribosomes, which does not exist in 70S ribosomes or 80S ribosomes homologous protein , the role of its combination with GTP is unknown.

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