Plays an important role in copper homeostasis by conferring tolerance to excess of copper and subclinical copper deficiency during vegetative stage. Can complement the yeast mutants atx1 and sod1. Binds 1 copper ion per subunit. Interacts with HMA5 and RAN1/HMA7. Induced by excess of copper (at protein level). No visible phenotype under normal growth conditions, but mutant plants have increased sensitivity to excess of copper. Over-expression of ATX1 confers increased tolerance to copper excess as well as subclinical copper deficiency (PubMed:22555879), but over-expressing plants are hypersensitive to severe copper deficiency (PubMed:22899077). Belongs to the ATX1 family. Extended N-terminus. Extended N-terminus. Extended N-terminus. Extended N-terminus.