"
Team:KULeuven/Project
From 2009.igem.org
Blue Light Receptor
The receptor senses the blue light to which the bacteria are exposed. By choosing the light intensity, the wanted vanillin concentration is set. Upon photo-excitation the receptorprotein YcgF dimerizes and interacts directly with the repressor YcgE. This protein is bound to the promoter-region of the key-gene and inhibits its transcription. The dimerized YcgF acts as an anti-repressor and releases YcgE from the DNA. Thereupon, the transcribed key activates vanillin production, which is proportional to the entered intensity of the blue light.
Vanillin Receptor
The vanillin receptor senses the vanillin concentration outside the cell. This information is needed to create the feedback loop that controls vanillin synthesis. The receptor consists of two proteins: virA and virG. In the presence of vanillin, virA binds a phosphor and transfers it to virG. In turn, the phosphorylated VirG binds to a so-called vir box sequence, triggering transcription of antikey. The more antikey is produced, the more it can anneal to the key and the less vanillin is produced. This process goes on until there’s an equilibrium between measured and wanted concentration.
Key Lock Antikey
The key/antikey system compares the signal from the blue light and vanillin receptor in order to control vanillin production. The more the measured amount of vanillin exceeds the wanted amount (set by the blue light intensity), the less vanillin is produced. After blue light irradiation, the key is transcribed and ‘unlocks’ the vanillin synthesis pathway. In response to the produced vanillin, the vanillin receptor then activates transcription of the antikey. Key and antikey are complementary RNA-strands: their annealing is favoured over the reaction between key en lock leading to vanillin synthesis.
Vanillin Production
A vanilla odour is created by synthesizing the molecule Vanillin. The starting point is tyrosine, an amino acid produced endogenously in E.coli. The subsequent pathway involves a combination of five enzymes. By locking both the transcription of the first and the third enzyme we prevent vanillin synthesis without the presence of the key.
Miss Blue Vanilla: CEO of the Fragrance Factory
Abstract
‘Essencia coli’ is a vanillin producing bacterium equipped with a control system that keeps the concentration of vanillin at a constant level. The showpiece of the project is the feedback mechanism. Vanillin synthesis is initiated by irradiation with blue light. The preferred concentration can be modulated using the intensity of that light. At the same time the bacterium measures the amount of vanillin outside the cell and controls its production to maintain the set point. The designed system is universal in nature and has therefore potential benefits in different areas. The concept can easily be applied to other flavours and odours. In fact, any application that requires a constant concentration of a molecular substance is possible.
