The role of TerW protein in the tellurite resistance of uropathogenic Escherichia coli

The ter operon, which is found on a large conjugative plasmid, pTE53, from the uropathogenic strain Escherichia coli KL53, mediates heavy metal ion resistance to tellurium compounds. Here we present the function of the terW gene, which is transcribed from its own promoter in the opposite direction to the terZABCDE loci and encodes a protein of 155 amino acids. A TerW protein containing an N-terminal His-tag was overexpressed, purified and analysed for the in vitro DNA-binding. Green fluorescent protein fusions, a fluorimetric assay, nonradioactive gel retardation and capillary electrophoresis footprinting were used to examine the interaction between the bioinformatically-predicted DNA-binding region and TerW. Here we show that TerW binds specifically to the potential promoter region of the terZABCDE genes, which are responsible for the tellurite resistance of the Escherichia coli host cells. Our results suggest that the transcriptional regulation of ter genes is operon-like.