Functional analysis of the heavy metal binding domains of the Zn/Cd-transporting ATPase, HMA2, in Arabidopsis thaliana.

• The Zn/Cd-transporting ATPase, HMA2, has N- and C-terminal domains that can bind Zn ions with high affinity. Mutant derivatives were generated to determine the significance of these domains to HMA2 function in planta. • Mutant derivatives, with and without a C-terminal GFP tag, were expressed from the HMA2 promoter in transgenic hma2,hma4, Zn-deficient, plants to test for functionality. • A deletion mutant lacking the C-terminal 244 amino acids rescued most of the hma2,hma4 Zn-deficiency phenotypes with the exception of embryo or seed development. Root-to-shoot Cd translocation was fully rescued. The GFP-tagged derivative was partially mis-localized in the root pericycle cells in which it was expressed. Deletion derivatives lacking the C-terminal 121 and 21 amino acids rescued all phenotypes and localized normally. N-terminal domain mutants localized normally but failed to complement the hma2,hma4 phenotypes. • These observations suggest that the N-terminal domain of HMA2 is essential for function in planta while the C-terminal domain, although not essential for function, may contain a signal important for the subcellular localization of the protein. [ABSTRACT FROM AUTHOR]