Figure 3. Light-dependent interaction between BlsA and binding partners.
To confirm that the interaction between BlsA and the binding partners BfmR and Fur was light-dependent, we used an on-column interaction assay. Samples of hexahistidine-tagged BlsA were incubated with either buffer (Control), untagged Fur, or untagged BfmR under dark (Dk) or light (Lt) conditions. After 30 minutes of incubation the solutions were run over Ni-NTA resin. The proteins that did not bind to the column were collected (FT) as was the proteins that eluted in 300 mM imidazole (Elut). Both Fur and BfmR appear to interact with BlsA in the dark (seen in the elution fraction) with a much higher affinity than when illuminated (little protein seen in the elution fractions when illuminated).