highly specialized ribosomes in mitochondria 13 different mRNAs: higher eukaryotes >100,000 different mRNAs
||Melnikov S et al., One core, two shells: bacterial and eukaryotic ribosomes. Nat Struct Mol Biol. 2012 Jun 5 19(6):560-7. doi: 10.1038/nsmb.2313. p.560 left column top paragraphPubMed ID22664983
|| Gruschke, S. & Ott, M. The polypeptide tunnel exit of the mitochondrial ribosome is tailored to meet the specific requirements of the organelle. Bioessays 32, 1050–1057 (2010). doi: 10.1002/bies.201000081.  Twiss, J.L. & Fainzilber, M. Ribosomes in axons–scrounging from the neighbors? Trends Cell Biol. 19, 236–243 (2009). doi: 10.1016/j.tcb.2009.02.007.PubMed ID20967780, 19359177
||p.560 left column top paragraph:"Despite the universal conservation of ribosomes, their composition varies considerably between different domains of life. For example, the ribosomal RNA/protein ratio may vary between 2:1 in bacterial ribosomes to 1:3 in some mitochondrial ribosomes, without substantial differences in molecular weights between the ribosomes. The molecular weight of the ribosomes may vary from 2.3 MDa in bacteria to 4.3 MDa in higher eukaryotes, without substantially changing the RNA/protein ratio. These differences are thought to reflect the functional divergence of ribosomes, the scope of which [investigators] are only beginning to uncover. For example, highly specialized ribosomes in mitochondria translate only 13 different mRNAs and are stably associated with membranes [primary source 1], whereas ribosomes from higher eukaryotes operate with more than 100,000 different templates and can be transported between different cell types [primary source 2]."