Fig. 2. Functionality of NarX–CyaA and NarL–CyaA hybrid proteins. (a) Sensor function of NarX–CyaA hybrids. NarX⁺, vector, NarX–T18 and NarX–T25 plasmids were introduced into strain VJS3041 [Φ(narG–lacZ) ΔnarX ΔnarQ] to monitor target operon activation. Cultures were grown in the absence or presence of nitrate (grey bars and black bars, respectively). Relative LacZ activity of 100 corresponds to 1890 Miller units. Controls: narX ⁺, WT narX gene on plasmid pVJS2474; tbl18 vector, plasmid pVJS5317; tbl25 vector, plasmid pKNT25.Error bars show sd of mean values determined from four independent assays. (b) Transcription activation function of NarL–CyaA hybrids. NarL⁺, vector, NarL–T18, NarL–T25 and tbl18–NarL plasmids were introduced into strain VJS9284 [Φ(napF _Hi–lacZ)₂₆₀ ΔnarL ΔnarP]. Cultures were grown in the absence or presence of nitrate (grey bars and black bars, respectively). Relative LacZ activity of 100 corresponds to 970 Miller units. Controls: narL ⁺, WT narL gene on plasmid pVJS4781; vector, plasmid pUT18. Results were mean values from two independent experiments, so sd values were not calculated.