Part:BBa_K3470006

Constitutive Promoter – RBS – MerR - PmerT promoter – GFP - Double Terminator 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) We test the response of MerR to methylmercury using this circuit Vs 2 control circuits which do not have the MerR gene present in them. E. coli cells inoculated with methylmercury chloride are grown for the required amount of time according to the results of the preliminary experiment. We check for GFP intensities expecting an exponential increase in fluorescence with an increase in methylmercury concentration for the circuit with MerR present. For the control with PmerT, transcription is initiated but at a lower level then the circuit to be tested. The plot of fluorescence and methylmercury concentration is taken. Exponential increase in fluorescence with an increase in methylmercury concentration in the case of the given circuit. The plot indicates that MerR contributes significantly in methylmercury response. Without MerR, even in the absence of methylmercury, transcription of downstream genes may occur 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