BosR directly binds to sequences upstream of the ospA and the ospD genes. (A) BosR binding to PospAB, PospD, PrpoS, PbicA, PbosR, PospC, Pech193, Pech818, and P53%G+C was analyzed by EMSA. Probes (1 nM) were first incubated with BosR (5 – 640 nM of dimer) and then separated on 6% polyacrylamide gels in 0.5× TBE. (B) BosR binding curves for PospAB (closed circle), PospD (closed square), PrpoS (closed triangle), PbicA (closed diamond), PbosR (open circle), PospC (open square), Pech193 or Pech818 (open triangle), and P53%G+C (open diamond) were generated based on quantification of the EMSA data shown in panel A. Fraction of probe bound by BosR in each reaction was calculated by dividing the intensity of all shifted bands (indicated with a bracket) with the total intensity of both the shifted bands and the unbound band (indicated with a line). In some probes, there were minor isomers (indicated with asterisks) that migrated slower and were often not recognized by BosR. These isomers were excluded in the quantitative analysis. For clarity, curves for the B. burgdorferi probes were indicated with solid lines, and curves for the non-B. burgdorferi probes were indicated with dashed lines.