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Prokaryotes perform transcription and translation much faster than eukaryotes. If memory serves, a single 70S prokaryotic ribosome can incorporate around 20 amino acids per second, whereas the 80S eukaryotic counterpart is much slower, at around 2 amino acids per second. Is the reason for this known? The only possibility I can think of is that prokaryotic mRNAs are often polycistronic, whereas eukaryotic mRNAs are not and tend to involve co-translational protein folding. Slower translation may be able to improve folding accuracy. Other than that, I can't think of any reason the 80S ribosome would be physically slower than the 70S ribosome. It's not like DNA replication where accuracy is exceedingly more important in multicellular organisms than in fast-replicating unicellular prokaryotes.

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  • $\begingroup$ I have made some minor corrections to your post. Ribosomes do not pump out amino acids, they form peptide bonds between them. (If they pump out anythng it is proteins.) Proteins cannot be polycistronic, only mRNAs or transcription units. There are poly-proteins, but mainly in eukaryotic viruses like polio. Your suggestion about folding is difficult to understand. Prokaryotic proteins are folded co-translationally just as eukaryotic ones are. $\endgroup$ – David Feb 5 '18 at 17:41
  • $\begingroup$ Transcription speed also varies across species. book.bionumbers.org/wp-content/uploads/2014/08/…. $\endgroup$ – com.prehensible Feb 5 '18 at 19:43
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Unless the poster can cite more recent papers to support the assertion regarding a difference in rates of prokaryotic and eukaryotic protein synthesis, I would say that this is incorrect.

Lacroute and Stent (1968) reported a rate of 15 amino acids per sec for β-galactosidase in Escherichia coli, whereas Knopf and Lamfrom (1965) reported a rate of 7 amino acids per sec for globin chains in rabbit reticulocytes. This does not appear much different to me, especially as a recent study by Li et al. (2014) showed that the rate of protein synthesis varies with the complexity of the assembly (if any) into which a protein is incorporated.

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  • $\begingroup$ My assertion mainly came from memory, and was reinforced by a quick search that showed a Quora question asking the same thing. Perhaps my memory was just mistaken! $\endgroup$ – forest Feb 6 '18 at 2:04
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    $\begingroup$ I can imagine circumstances (growth on rich medium) where bacterial protein synthesis is faster, and I need to comb through the suplementary material in the Li paper to see if I can find an update on the 60s figures. When I've done that I'll post an addendum, also discussing what might be rate-limiting for translation. $\endgroup$ – David Feb 6 '18 at 10:35

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