From 2009.igem.org
Blue Light Receptor
This receptor senses the intensity of blue light. By exposing the bacteria to a certain intensity of blue light we enter the wanted vanillin concentration. The receptor contains a protein, YcgF. Upon photo-excitation it dimerizes and acts as an anti-repressor for an other protein, YcgE. YcgE is bound to the promotor-region and inhibits transcription. The dimerized YcgF binds with the repressor, releasing it from the DNA and allowing transcription. this way the transcribed component is proportional to the intensity of blue light.
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