Zinc dependence of zinT (yodA) mutants and binding of zinc, cadmium and mercury by ZinT

ZinT (B1973), previously known as YodA, was originally characterised as a cadmium-induced periplasmic protein under the regulation of Fur and SoxS. Here we describe a decrease in zinT transcript in response to elevated copper concentrations and the zinc and copper dependent phenotype of a ΔzinT strain. Cadmium sensitivity of the ΔzinT strain was not observed. We demonstrate the binding of nickel, zinc, cadmium, and mercury, but not cobalt, copper, iron, and manganese, to purified ZinT using mass spectrometry. This and previous studies support the hypothesis that ZinT plays a role in zinc homeostasis and is required for growth under zinc limited conditions, suggesting that ZinT is either a periplasmic zinc chaperone or is involved in zinc import. Limited metal ion discrimination results in regulation of PzinT in a non-specific manner, which is mirrored in the binding of several different heavy metals by ZinT.