Vanillin Receptor: Design
The vanillin receptor senses the vanillin concentration outside the cell. This information is needed to create the feedback loop that controls vanillin synthesis.
Certain virulent bacteria like Agrobacterium Tumefaciens contain a large tumor-inducing plasmid that carries different virulence (vir) genes. The vanillin receptor is composed of two of those vir genes: virA BBa_K238008 and virG BBa_K238009. rpoA (BBa_K238010) is an alfa subunit polymerase that helps virG work in E. coli. These three genes are constitutively transcribed under promoter BBa_J23110. The terminator is BBa_B0015 and BBa_B0032 is chosen as RBS.
Together, virA and virG form a two component system that recognizes phenol derivatives like vanillin and other signals like low pH, certain aldose monosaccharides and limited phosphate. Under the influence of vanillin, virA is autophosphorylated. The virA dimers function as a sensor kinase. They process all the input signals and phosphorylate virG. VirG then binds to a vir box sequence located in the virB promoter region BBa_K238011 and triggers the transcription of antikey BBa_K238005.