Figure 4. Site-directed mutagenesis identifies DNA-binding residues within ChxR.

A, Alanine substitutions were generated in several of the residues within regions (α5–α6 and β11–β12) known to interact with DNA in other OmpR/PhoB subfamily members. Representative EMSA of IR800-labeled DNA in the absence of ChxR (-) and in the presence of 44 μM wild-type ChxR or 44 μM ChxR^H186A. B, The amount of DNA shifted with each substitution was quantified. DNA binding of four substitutions (Asn182, His186, Lys192, and Arg205) was significantly (p<0.001 (***)) reduced relative to wild-type ChxR.