Ribosomes can read mRNA and produce proteins, if we somehow make a circular mRNA for the ribosome to bind onto, it will make infinitely long "proteins", (since ribosomes can make very big proteins, I assume they can bind long enough before disassociating) However after doing some search on this topic, it seems that I am able to find only about 2 related papers. One of them seems to be from 1998, while the other one is more recent.

These articles suggest that it's doable. If this works, we'll be able to produce biopolymers with the sequence exactly as we designed, there would be massive applications, but I'm curious why it's not getting much attention, or why aren't there more papers related to this area?

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    $\begingroup$ Non-covalent circularization is known to increase the protein steady state levels by increasing mRNA stability and translation efficiency. But certainly no long proteins are made by such a process. If there is no stop codon then the non-stop decay mechanism eliminates the mRNA. I am not sure how it works out in this case. I guess it may work out to some extent but is not very reliable. $\endgroup$ – WYSIWYG Mar 3 '14 at 3:37
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    $\begingroup$ If you read the two papers, in fact long proteins are made. They stated that they constructed a circular mRNA with infinite open reading frame. The 1998 papers makes poly-GFP 5~6 times long than the GFP (if i remember correctly). The 2013 paper makes very large proteins as can be seen on the southern blotting figures (i didn't find the numbers though). I'm however curious about how the non-stop decay mechanism works. In the paper they used the PURE system, which is an artificially constructed reaction vessel that mimics the environment within the cell, but eliminates the decay mechanisms. $\endgroup$ – seilgu Mar 3 '14 at 6:38
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    $\begingroup$ Yes I did see the paper; I found it interesting. But I am not sure if this can be reliably replicated and how the length of the product can be controlled. Perhaps those are the aspects that you are interested in when you plan to use the system to synthesize your biopolymer. (PS: it is the western blotting that is used for detecting the protein) $\endgroup$ – WYSIWYG Mar 3 '14 at 7:32
  • $\begingroup$ Yeah, western blotting, sorry for the mistake. $\endgroup$ – seilgu Mar 4 '14 at 6:06
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    $\begingroup$ I'm familiar with those papers, and they were dissapointed in the yields. The issue seems to be that ribosome binding is the slow step, and the ribosomes don't stay on the mRNA forever. Made me wonder if you could tie the ribosome around the mRNA strand to lock it in place. $\endgroup$ – user137 Dec 26 '14 at 5:20

In vitro translation is not as efficient as other chemical polymer reactions. For example, when proteins are synthesized using in vitro translation systems, many researchers have been using radio-labeling to see the products because the yield is too low to detect them by other methods, although few small proteins have been successfully produced at a microgram level. It should be noted that it is also difficult to produce exogenous long peptides at sizes more than 100kDa in E coli in vivo expression system.


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