Fig. 4: VirB requires CTP- and virS binding to accumulate on DNA in high-stringency conditions.
a Biolayer interferometry analysis of the interaction of VirB with virS-containing DNA (215 bp) in high-stringency buffer (500 mM NaCl). Biosensors carrying a double-biotinylated, virS-containing DNA fragment (at a density corresponding to a wavelength shift of ~0.5 nm) were probed with VirB (20 µM) in the absence or presence of CTP (1 mM). The virS sequence used is shown at the top. The graph shows the results of a representative experiment (n = 3 independent replicates). b Same as in panel a, using a DNA fragment with a scrambled virS site. c Titration of double-biotinylated virS-containing DNA (215 bp) with increasing concentrations of VirB in the presence of CTP (1 mM) in high-stringency buffer (500 mM NaCl). DNA was immobilized as described in panel A. d DNA-binding affinity of VirB in high-stringency conditions. The maximal wavelength shifts measured at equilibrium in the traces shown in panel c were plotted against the corresponding VirB concentrations. Error bars indicate the SD (n = 3 independent replicates). A one-site-specific-binding model was used to fit the data. The calculated KD value is given in the graph. Source data are provided as a Source Data file.
