Figure 6
Schematic of aspartate sensor coupled to the positive-feedback amplifier. The two-component sensor consists of the Taz sensor kinase and the OmpR response regulator. Taz controls the level of phosphorylated OmpR (OmpR-P), which in turn activates the expression from the P ompC promoter. When the Taz sensor kinase is bound with aspartate, it increases the levels of OmpR-P, leading to increased expression from the P ompC promoter. In our design, the Taz sensor kinase has been cloned behind the constitutive P LtetO-1 promoter on one plasmid (the cells used in these experiments do not possess TetR). On a second plasmid, LuxRΔ2-162 has been cloned behind the P ompC promoter, resulting in the expression of LuxRΔ2-162 being aspartate dependent. The third plasmid harbors the positive feedback amplifier. The sensor was coupled to the amplifier by transforming the three plasmids into a ΔenvZ null mutant (GN101).