Figure 2.

Models for natural and artificial cad operons. (A) Model for natural cad operon-encoded cadmium resistance of Pseudomonas putida 06909. The model involves the following proteins: CadR, which is related to the MerR family of response regulators; CadA, a cadmium-transporting ATPase; LysR, a LysR family response regulator, which may be involved in bacterium-fungus interactions. (B) Models for artificial cad operon-encoded bioindication and biosorption of Cd(II). The models involve the following proteins: Lpp-OmpA-CdBD, an outer membrane anchoring chimera protein for surface display of metal binding domain derived from CadR; mCherry and eGFP, fluorescent reporters; lacZα, an enzymatic reporter which is expressed under the control of cad promoter driven by Cd(II), and lacZM15, a protein that is synthesized under the control of host lac promoter driven by IPTG. After active tetrameric β-galactosidase is finally assembled, enzymatic activity is then determined.