Fig. 4.

Cooperation of 2 sites triggers the specific selectivity of cadmium ions. (A) Cadmium sensitivity study using the luxAB reporter system in vivo. CadR^WT (black) and its variants, CadR^N81A (a, blue), CadR^{C77S/C112S/C119S} (b, orange), and CadR^H87A/H90A (c, green) are tested. Error bars represent SD. (B) The scaffold of the MBD in CadR^WT and CadR^H87A/H90A. Glu62 in the DBD is omitted for clarity. Site I and site II are shown as red and magenta circles, respectively. The coordination bonds are shown as dashed lines. (C) A putative model of the partially distorted state promoter (cyan) between the repressor state (magenta) and activator state (yellow). The σ factor and core enzyme of RNAP are colored in marine and gray, respectively. The −10 and −35 elements are indicated by the orange mesh.