Functional analysis of the Escherichia coli zinc transporter ZitB

The membrane transporter ZitB responsible for Zn(II) efflux in Escherichia coli was studied by site-directed mutagenesis to elucidate the function of individual amino acid residues. Substitutions of several charged or polar residues, H53, H159, D163 and D186, located in predicted transmembrane domains resulted in loss of ZitB function. In contrast, neither the amino-terminal nor the carboxy-terminal regions, both histidine-rich, were required for function.