Part:BBa_K3470006

Circuit

Constitutive Promoter – RBS – MerR - PmerT promoter – GFP - Double Terminator

Usage and Biology

MerR is a homodimer and the regulatory factor of the mer operon. It acts as an activator in the presence of Hg (II) and a weak repressor in its absence, maintaining its expression at a certain level. It binds to the operator site between –35 and –10 elements of mercury inducible promoter PmerT, independent of the presence of mercury. The Hg- bound MerR dimer causes a structural distortion of PmerT, which allows the RNA polymerase to bind, leading to the transcription of genes downstream to it.(Hobman, J. L., Wilkie, J., & Brown, N. L. 2005)

Proposed experimentation

The response of MerR to methylmercury using this circuit Vs 2 control circuits which do not have the MerR gene present in them must be tested. E. coli cells inoculated with methylmercury chloride must be grown for the required amount of time according to the results of the preliminary experiment. GFP intensities should be mapped, where an exponential increase in fluorescence with an increase in methylmercury concentration for the circuit with MerR present is expected.

For the control with PmerT, transcription is expected to be initiated but at a significantly lower level than the circuit to be tested. The plot of fluorescence and methylmercury concentration must be drawn. It is expected that there would be an exponential increase in fluorescence with an increase in methylmercury concentration in the case of the given circuit. The plot is expected to indicate that MerR contributes significantly to methylmercury response. However, without MerR, even in the absence of methylmercury, transcription of downstream genes is expected to occur in significantly low amounts with the help of PmerT.

References

Brown, N. L., Stoyanov, J. V., Kidd, S. P., & Hobman, J. L. (2003). The MerR family of transcriptional regulators. FEMS Microbiology Reviews, 27(2–3), 145–163. https://doi.org/10.1016/S0168-6445(03)00051-2

Hobman, J. L., Wilkie, J., & Brown, N. L. (2005). A design for life: Prokaryotic metal-binding MerR family regulators. BioMetals, 18(4), 429–436. https://doi.org/10.1007/s10534-005-3717-7