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: You have a reasonable point that you can be nice to people inside a conversation but (possibly inadvertently) non-nice to those outside it. I think niceness within conversations is more important, as people outside them can more easily choose not to participate in them, but this doesn't work excellently. Banning discussion of anything some people do not like reading is *a* fix for some of this, but I don't like the tradeoffs, given the wide range of things in this category. Isolating that elsewhere is also not good for various reasons I indicated before. A generalized rule-4-y approach could end up doing basically the same thing as preemptively banning it, and people seem dissatisfied with "ignore the channel for a bit". Thus, I'm unsure of how the issue can be solved nicely and it's worth actually investigating the options.
gollark: What a strange name.
gollark: You are to wait while I:- type- think- move a mouse cursor around somewhat- get distracted by unrelated topics repeatedly
gollark: Too bad, you are to wait.
gollark: Somewhat, maybe. Please hold on while I engage in typing™.

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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