Fig 4.

Electrophoretic mobility shift assays for determination of GenR binding sites upstream of the genDFM, genR, and genKH operons. (A and B) Effects of 3-HBA and GEN on the binding affinity of GenR for the upstream regions of genDFM, genR, and genKH operons. The probes for genDFM (DFMan in A), genR, and genKH operons (R-KHan in B) were incubated with increasing amounts of His₆-GenR while the amounts of GEN and 3-HBA remained constant. The concentrations (nM) of purified His₆-GenR are indicated by numbers in parentheses, either with (+) or without (−) 300 nM GEN and 3-HBA. Glucose served as a control. Each lane contained 0.5 ng (0.3 to 0.4 nM) of ³²P-labeled DFMan and R-KHan probes. The free probes are indicated by open arrows, and the retarded DNA fragments are indicated by solid arrows.