Evidence for zinc and cadmium binding in a CDF transporter lacking the cytoplasmic domain

► MmCDF3 selectively binds zinc and cadmium at two binding sites. ► Removal of His-tag is vital for maintaining CDF function. ► An extended N-terminus may act as an alternative “B” binding site in truncated CDFs. ► Zn2+ binding is inhibited by the presence of Cd2+ suggesting shared binding sites.