FIG. 3.

KapK-NirA in vivo interaction at the NirA binding site in the niiA-niaD promoter. ChIP using anti-S-tag antibody directed against S-tagged KapK and amplifying precipitated DNA at the NirA binding site 2 in the niiA-niaD intergenic region. Nitrate-induced cultures were submitted to repression by a shift to ammonium-containing medium, and samples were taken immediately before the shift (0 min) and after 10 min (10) and 30 min (30) of incubation, respectively. Relative amounts of precipitated DNA compared to input DNA (for details see Materials and Methods) at two time points of repression are shown. ChIP reactions with the anti-S-tag antibody in a strain lacking the S-tag epitope at the kapK locus (contr) were used as controls for background amplification. Error bars indicate the standard deviations of at least three biological replicates.