Behind the shield of Czc: ZntR controls expression of the gene for the zinc-exporting P-type ATPase ZntA in .

In the metallophilic beta-proteobacterium , the plasmid-encoded Czc metal homeostasis system adjusts the periplasmic zinc, cobalt and cadmium concentration, which influences subsequent uptake of these metals into the cytoplasm. Behind this shield, the P-type APTase ZntA is responsible for removal of surplus cytoplasmic zinc ions, thereby providing a second level of defense against toxic zinc concentrations. ZntA is the counterpart to the Zur-regulated zinc uptake system ZupT and other import systems; however, the regulator of expression was unknown.