Mitochondrial ribosome

Mitochondrial ribosome or mitoribosome is a protein complex that is active in mitochondria and functions as a riboprotein for translating mitochondrial mRNAs encoded in mtDNA. Mitoribosomes, like cytoplasmic ribosomes, consist of two subunits — large (mtLSU) and small (mt-SSU).[1] However, the ratio of rRNA/protein is different from cytoplasmic ribosomes, mitoribosomes consist of several specific proteins and less rRNAs.[1]

A diagram showing mtDNA (circular) and mitochondrial ribosomes among other mitochondria structures

Function

Mitochondria contain around 1000 proteins in yeast and 1500 proteins in humans; however only 8 and 13 proteins are encoded in mitochondrial DNA in yeast and human, respectively. Most mitochondrial proteins are synthesized via cytoplasmic ribosomes.[2] Proteins that are the key components in the electron transport chain are translated in mitochondria.[3][4]

Structure

Mammalian mitoribosomes have small 28S and large 39S subunits, together forming a 55S mitoribosome.[5]

Genes
gollark: One alternative interpretation I read somewhere was coordination problems - people don't do much because they feel like it won't be useful unless other people also do.
gollark: I'm not saying that they shouldn't care, to clarify, but that people don't, telling them their preferences are wrong is not really a winning strategy, and the lack of concern of most richer countries for poorer ones reflects most people's demonstrated attitudes.
gollark: Yes, exactly.
gollark: (also, global prosperity is generally going up, illiteracy & extreme poverty going down, etc.)
gollark: Anyway, I find those "various people die of easily preventable deaths → capitalism bad" things unreasonable. I suspect most people don't actually *care* about random people somewhere dying, given the fact that you can quite easily donate to very effective charities for e.g. helping fix malaria under the existing system, and yet nobody does this.

References
  1. Alexey Amunts; Alan Brown; Jaan Toots; Sjors H. W. Scheres; V. Ramakrishnan (2015). "Ribosome. The structure of the human mitochondrial ribosome". Science. 348 (6230): 95–98. doi:10.1126/science.aaa1193. PMC 4501431. PMID 25838379.
  2. Wenz, Lena-Sophie; Opaliński, Łukasz; Wiedemann, Nils; Becker, Thomas (2015). "Cooperation of protein machineries in mitochondrial protein sorting". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 1853 (5): 1119–1129. doi:10.1016/j.bbamcr.2015.01.012. ISSN 0167-4889. PMID 25633533.
  3. Johnston, Iain G.; Williams, Ben P. (2016). "Evolutionary Inference across Eukaryotes Identifies Specific Pressures Favoring Mitochondrial Gene Retention". Cell Systems. 2 (2): 101–111. doi:10.1016/j.cels.2016.01.013. ISSN 2405-4712. PMID 27135164.
  4. Hamers, Laurel (2016). "Why do our cell's power plants have their own DNA?". Science. doi:10.1126/science.aaf4083. ISSN 0036-8075.
  5. Basil J. Greber; Philipp Bieri; Marc Leibundgut; Alexander Leitner; Ruedi Aebersold; Daniel Boehringer; Nenad Ban (2015). "Ribosome. The complete structure of the 55S mammalian mitochondrial ribosome". Science. 348 (6232): 303–308. doi:10.1126/science.aaa3872. hdl:20.500.11850/100390. PMID 25837512.


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