Expression of ZntA, a zinc-transporting P₁-type ATPase, is specifically regulated by zinc and cadmium

All cells have developed various mechanisms to regulate precisely the availability of important micronutrients such as zinc and copper; in many cells, this regulation is mediated by P₁-type ATPases. Most of the P₁- ATPases have been described very recently, and little is known about their molecular mechanism and regulation. Here, we demonstrate that the expression of ZntA, a Zn,Cd-transporting P-type ATPase of Escherichia coli, is specifically regulated by the transported cations, cadmium and zinc. Nickel, cobalt, and copper did not induce the expression of ZntA, even when present at concentrations as high as 0.6-1 mM. The effect of zinc and cadmium on the ZntA expression is concentration dependent, the apparent K(m) for Cd (19 μM) being markedly lower than that for Zn (100 μM). This metal selectivity is opposite to the known metal selectivity of transport by ZntA. Thus, we speculate that, to maintain zinc concentrations in the cell in the presence of cadmium, ZntA probably interacts with other proteins that modulate the ZntA selectivity towards transported cations.