Effect of ArgR on protection of the gltBDF promoter by RNAP and Lrp. The first 4 lanes represent the sequencing ladder of the region. A. A gltBDF DNA fragment from -462 to +161 labeled at the -462 end was used. The concentrations of both Lrp and ArgR were 25 nM. B. A fragment of gltBDF DNA from -571 to +51, labeled at the +51 end was used. The concentrations of proteins used were as follows: ArgR 25 nM, RNAP 50 nM, Lrp 25 nM and IHF 50 nM. Reactions contained 5 mM L-arginine.