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The Paris Saclay 2014 team chose to use chromoproteins to express these colours in ''E. coli''. Chromoproteins are reflective proteins that contain a pigmented prosthetic group and do not need to be excited to be seen. They fused a yellow chromoprotein with a blue one in order to display a green color. This construction is referred as the green fusion chromoprotein. In order to make the bacteria ripe like a real lemon, they decided to take advantage of the fusion protein’s design by using a translational suppression system. They added an amber codon (stop codon) within the linker separating the yellow and the blue chromoproteins genes. Therefore, the suppressor tRNA will suppress amber codon allowing the translation of the green fusion chromoprotein in presence of salicylate. Conversely, the down regulation of the suppressor tRNA in absence of salicylate will allow bacteria switch from green to yellow, thus simulating the ripening of a real lemon. This system is referred to as the colour switch system. | The Paris Saclay 2014 team chose to use chromoproteins to express these colours in ''E. coli''. Chromoproteins are reflective proteins that contain a pigmented prosthetic group and do not need to be excited to be seen. They fused a yellow chromoprotein with a blue one in order to display a green color. This construction is referred as the green fusion chromoprotein. In order to make the bacteria ripe like a real lemon, they decided to take advantage of the fusion protein’s design by using a translational suppression system. They added an amber codon (stop codon) within the linker separating the yellow and the blue chromoproteins genes. Therefore, the suppressor tRNA will suppress amber codon allowing the translation of the green fusion chromoprotein in presence of salicylate. Conversely, the down regulation of the suppressor tRNA in absence of salicylate will allow bacteria switch from green to yellow, thus simulating the ripening of a real lemon. This system is referred to as the colour switch system. | ||
− | [[File:T--Paris_Saclay--project_2014_1.jpeg.png|400px|thumb|centre| | + | [[File:T--Paris_Saclay--project_2014_1.jpeg.png|400px|thumb|centre|Schema of the lemon ripening project]] |
The tRNA used is the supD suppressor tRNA. It has been placed under control of a salicylate inducible promoter Psal. Its role is to suppress the introduced amber codon. The nahR gene encodes a transcriptional regulator that is induced by salicylate and thus binds nah or Psal promoters. In presence of high salicylate concentration in the agar media, supD will be expressed and so the green fusion chromoprotein: bacteria will display a green color. However, as bacteria grow into agar, less salicylate will remain available into the media. Thus, the decrease of the nahR-salicylate complex amount within bacteria will lead to supD downregulation through time. In turn, decrease of supD amount will result in less codon readthrough and so less translation of the green fusion protein and more translation of the yellow chromoprotein. As a result, bacteria will gradually change from green to yellow. | The tRNA used is the supD suppressor tRNA. It has been placed under control of a salicylate inducible promoter Psal. Its role is to suppress the introduced amber codon. The nahR gene encodes a transcriptional regulator that is induced by salicylate and thus binds nah or Psal promoters. In presence of high salicylate concentration in the agar media, supD will be expressed and so the green fusion chromoprotein: bacteria will display a green color. However, as bacteria grow into agar, less salicylate will remain available into the media. Thus, the decrease of the nahR-salicylate complex amount within bacteria will lead to supD downregulation through time. In turn, decrease of supD amount will result in less codon readthrough and so less translation of the green fusion protein and more translation of the yellow chromoprotein. As a result, bacteria will gradually change from green to yellow. | ||
− | [[File:T--Paris_Saclay--project_2014_2.jpeg|400px|thumb|centre| | + | [[File:T--Paris_Saclay--project_2014_2.jpeg|400px|thumb|centre|Explanatory diagram of the lemon ripening]] |
==Characterization== | ==Characterization== |
Revision as of 13:13, 15 October 2016