Our Project is divided into three sub-projects, the uric acid detector, the uric acid decomposer and the uric acid transporter, and they are mentioned in the page of project description. These three BioBricks enclose the same promoter, and the mechanism of it will be explained below.
Mechanism of the Uric Acid Concentration-Sensitive Promoter
The promoter is designed to be sensitive to the concentration of uric acid. This promoter controls the expression of the downstream gene and its session consists of a constitutive promoter J23100, a RBS B0034, a strong repressor KRAB-HucR and a double terminator B0015. HucR is itself a repressor. Its repressing ability is enhanced by KRAB. The resulting repressor is a chimeric mammalian urate-dependent transsilencer (mUTS).
HucO is an operative site for mUTS to bind into. When mUTS is binded to hucO, the expression of downstream gene is restricted according to the concentration of substrates. The presence of uric acid limits the binding of mUTS to hucO. The limitation varies as the concentration of uric acid.
mUTS binds to hucO and GFP is not expressed when uric acid is absent or at very low concentration. Alternatively, the complex detaches from hucO and GFP is expressed according to the concentration of uric acid.
: Christian Kemmer, Marc Gitzinger, Marie Daoud-El Baba, Valentin Djonov, Jorg Stelling & Martin Fussenegger (2010) Self-sufficient control of urate homeostasis in mice by a synthetic circuit. Nature Biotechnology doi: 10.1038/nbt.1617