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From 2013.igem.org

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Sensor

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Xenobiotics Sensor

The sensor consists in the application of the model development by Debrecen in 2010, using nuclear receptors as transcriptional factors1 . The family of nuclear receptors are composed by a series of proteins which acts like sensor for lipids, steroids, hormones,endocrine-disrupting chemicals, etc.2

Several xenobiotic substances are present in the intestine and many of them result toxic for the host. One example is organochlorine pesticide, a endocrine-disrupting chemical, which is a molecule that can be found on contaminated food and represent an important toxicity source. Detection and decrease levels of pesticide could be an effective way to solve the problem .3

Nuclear receptors are ligand specific, and are composed by two basis domains: ligand binding domain (LBD) and DNA binding domain (DBD).2 In our sensor we adapt and characterized Debrecen system, which fuses specific LBD with Gal 4 DBD. 1

The system adapt TRE-CMV promoter; that has a basal expression in the absence of TetR, Gal 4; yeast transcription factor galactose 4, PXR ligand binding domain which binds organochlorine and PolyA; important for nuclear export. The complete system will be expressed in one plasmid. 1

Finally the nuclear receptor will interact with UAS, using Gal4 as specific binding region. UAS and Gal-4 forms a complex which activate the expression of the L.plantarum promoter. Development of specific nuclear receptors helps to quantify accurately the expression of the report product in relation with the ligand concentration. 4

The probiotic sensor detect organochlorine, then the nuclear receptor complex activates the promoter for the expression of linA enzyme, which catalyze the conversion of γ-hexachlorocyclohexane to 1,2,4-trichloro benzene.5Using this method our probiotic is not only available to detect organochlorine pesticides but also degrade capabilities of the molecule, contributed to decrease the presence of the toxic molecule .

REFERENCES

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1.iGEM Debrecen (2010).Recovered from https://2010.igem.org/Team:Debrecen-Hungary/favorite

2. Willson, T. et al.(2002) PXR, CAR and drug metabolism. Nature Publishing group: Volume 1

3.Kojima, H, et al. (2010). Endocrine- disrupting potential of pesticides via nuclear receptors and aryl hidrocarbon receptor. Journal of health science.

4. Elliot, D. & Brand A. (2002) The Gal4 system. Methods in molecular biology in Drosophila: A Fly Geneticist's Swiss Army Knife.

5.Yang, J, (2011). Construction of a Genetically Engineered Microorganism that Simultaneously Degrades Organochlorine and Organophosphate Pesticides. Appl Biochem Biotechnol.