Figure 8.

Analysis of guanidine sensing by a riboswitch lacZ reporter. (a) Schematic representation of the assay for the riboswitch lacZ reporter using the standard Miller assay, which detects expression of β-galactosidase using the colorimetric substrate ortho-nitrophenyl-β-galactoside (ONPG). (b) β-Galactosidase reporter gene expression in Miller Units (MU) as controlled by Kpn-WT and Kpn-M4 riboswitches with different concentrations of guanidine. (c) Plot of guanidine reporter response (ΔMU/MU) over time after addition of 50 mM guanidine at time 0. Data shown are the average with a standard deviation of three biological replicates.