The functional analysis of directed amino-acid alterations in ZntR from Escherichia coli

The ZntR protein from Escherichia coli is a member of the MerR-family of transcriptional regulatory proteins and acts as a hyper-sensitive transcriptional switch primarily in response to Zn(II) and Cd(II). The binding of metal-ions to ZntR initiates a mechanism that remodels the cognate promoter, increasing its affinity for RNA polymerase. We have introduced site-directed mutations into zntR and shown that cysteine and histidine residues are important for transcriptional control and have an effect on metal-ion preference, sensitivity and magnitude of induction. We propose a three-dimensional model of the N-terminal region of ZntR based upon the coordinates of the MerR-family regulator BmrR.