FIG. 3.

Activity of Pm when mediated by different XylS variants, overexpressed from the Ptet* promoter, in the presence or absence of meta-toluate. Transparent boxes on the diagram indicate the putative domains of XylS. Asterisks indicate the N-terminal tags, and gray boxes within the C-terminal domain indicate the putative helix-turn-helix regions. The hybrid XylS variants contain insertions of the hinge region of BPV E2 protein (lines 18 and 19), a synthetic Gly-Ala-rich region (lines 20 and 21), and the dimerization domain of the λCI protein (lines 22, 23, and 24) of E. coli CC118Pm-lacZ was transformed with plasmids for expression of XylS variants from the Ptet* promoter. Bacteria were grown in LB medium overnight, diluted 1:100 in the same medium in the absence (−mtol) or presence (+mtol) of 1 mM meta-toluate, and β-Gal levels were determined after 4 h. The values in Miller units are the averages of results from three to six assays. Error bars indicate the standard deviations.