Team:Cambridge/Bioluminescence/Background

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(Regulation by LuxR and LuxI)
(Regulation by LuxR and LuxI)
 
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==Regulation by LuxR and LuxI==
==Regulation by LuxR and LuxI==
{{:Team:Cambridge/Templates/RightImage|image=LuxRI.jpg|caption=Transcriptional induction of gene expression by LuxR + AHL}}
{{:Team:Cambridge/Templates/RightImage|image=LuxRI.jpg|caption=Transcriptional induction of gene expression by LuxR + AHL}}
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LuxR and LuxI are genes involved in the quorum sensing mechanism of Vibrio fischeri. LuxI codes for an enzyme catalysing the synthesis of a specific N-acyl homoserine lactone (AHL). This compound is diffusible and acts as a signal between different cells of the population. In nature, V. fischeri uses quorum sensing to assess the size of the symbiont colony within their host organism. At the right colony density they activate bioluminescence. AHL binds to the protein product of LuxR changing its 3-dimensional shape ([http://jb.asm.org/cgi/content/short/179/2/557 Stevens and Greenberg 1997]). The C-terminal domain of the activated LuxR then interacts with H-NS proteins bound to curved DNA-regions in the Lux operon. Such regions are especially prominent in the promoter regions of LuxI and LuxR, causing AHL to induce its own synthesis. Repression also occurs at the LuxCDABEG promoter as well as within the coding sequence of LuxC, LuxA and LuxB. While the natural quorum-controlled mechanism relieves this repression, it remains a problem if the lux operon is placed under a different promoter in a H-NS wild type strain.
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LuxR and LuxI are genes involved in the quorum sensing mechanism of Vibrio fischeri. LuxI codes for an enzyme catalysing the synthesis of a specific N-acyl homoserine lactone (AHL). This compound is diffusible and acts as a signal between different cells of the population. In nature, V. fischeri uses quorum sensing to assess the size of the symbiont colony within their host organism. At the right colony density they activate bioluminescence.  
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AHL binds to the protein product of LuxR changing its 3-dimensional shape ([http://jb.asm.org/cgi/content/short/179/2/557 Stevens and Greenberg 1997]). The C-terminal domain of the activated LuxR then interacts with H-NS proteins bound to curved DNA-regions in the Lux operon. Such regions are especially prominent in the promoter regions of LuxI and LuxR, causing AHL to induce its own synthesis. Repression also occurs at the LuxCDABEG promoter as well as within the coding sequence of LuxC, LuxA and LuxB. While the natural quorum-controlled mechanism relieves this repression, it remains a problem if the lux operon is placed under a different promoter in a H-NS wild type strain.
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Latest revision as of 18:19, 27 October 2010