DNAse I protection of the gltBDF promoter region by Lrp, IHF, and RNA polymerase. A. DNase I protection assay of gltBDF promoter region in the presence of both Lrp and IHF. A fragment of gltB DNA from -325 to +8 was used in the reaction. The first 4 lanes represent a sequencing ladder of the region. In all cases where it was added, Lrp was used at 2 nM. The amounts of IHF are shown in nM. B. A fragment of gltB DNA from -571 to +51, labeled at the +51 end of the template strand using 32P, was used. When present, the concentration of RNAP was 30 nM, Lrp 100 nM and IHF 100 nM. The first 4 lanes represent a sequencing ladder of the template strand of the region.