Cadmium pollution in the food chain has become a monumental public health concern since the emergence of the first serious cadmium-related disease (Itai-Itai disease) in Japan. Examination of a rare biological function of cadmium showed that the cadmium ion acts as a catalysis center of carbonic anhydrase in marine diatoms at low zinc levels. Organisms have evolved multiple detoxification systems to eliminate the toxicity of cadmium. These detoxification systems can detoxify other heavy metal ions besides cadmium, such as lead or mercury. Pseudomonas putida CadR belongs to the MerR family of transcriptional regulators, which regulates its own transcription and the transcription of a cadmium efflux P-type ATPase CadA. The molecular basis underlying the specific cadmium selectivity of CadR remains elusive, however. The previously reported MerR family homologs possess remarkable metal sensitivity and selectivity; for instance, CueR can respond to free Cu(I) at zeptomolar concentrations. These metal-binding properties are typically achieved by the unique coordination geometry in a binding site, such as the linear CuS2 in CueR. Here you can see a unique crystal structure of the CadR regulator from Pseudomonas putida in complex with Cd ions (spheres) and a synthetic DNA containing the regulated promoter sequence. This is an excellent example on how structural biology can contribute to the dissection of complex molecular mechanisms (PDB code: 6JGX)

#molecularart ... #immolecular ... #cadmium ... #ion ... #detoxification ... #coordination ... #cadR ... #promoter ... #geneexpression ... #xray

Structure of CadR complex rendered with @proteinimaging and depicted with @corelphotopaint