Fig. 6
From: Evolution of transcriptional regulation of histidine metabolism in Gram-positive bacteria
DNA binding assay of HisR regulator from Ruminococcus gnavus. Fluorescence polarization binding assay of HisR protein to cognate DNA site upstream of the hisX gene in R. gnavus and the influence of L-histidine on protein-DNA binding. DNA–protein complex formation was monitored by an increase in the fluorescence polarization (FP) value. The error bars indicate standard deviations of triplicate values. Increasing concentrations of HisR protein were mixed with a 30-bp fluorescence-labeled DNA fragment of the hisX gene promoter region. 0.75 mM of L-histidine added to the preincubation mixture improved the protein-DNA interaction