FIG. 1.

Gel mobility shift assay of the fxbA-IdeR interaction. The ability of IdeR to bind to the fxbA regulatory region was measured by acrylamide gel electrophoresis of protein-DNA complexes. Approximately 10 fmol of a 126-bp ³²P-labeled fragment containing the regulatory region of fxbA was incubated with no metal or with 200 μM Ni²⁺ or Fe²⁺ and increasing amounts of IdeR from 0 to 18 pmol, as indicated above the lanes. Lane 1 contained the DNA alone, and lane 2 had the DNA and 18 pmol of IdeR with no metal. Binding conditions and gel electrophoresis are described in Materials and Methods.