Disease relevance of ZAT

• To obtain evidence for the postulated function of the Arabidopsis gene, transgenic plants with the ZAT coding sequence under control of the cauliflower mosaic virus 35S promoter were analyzed [1].
• RNA interference-mediated silencing of AtMTP1 causes Zn hypersensitivity and a reduction in Zn concentrations in vegetative plant tissues [2].
• ZAT1p functioned as an uptake system for 65Zn2+ in two strains of the Gram-negative bacterium Ralstonia metallidurans, which were different in their content of zinc-efflux systems [3].
• When heterologously expressed in Escherichia coli, ZAT1p bound zinc in a metal blot [3].

High impact information on ZAT

• Poplar metal tolerance protein 1 confers zinc tolerance and is an oligomeric vacuolar zinc transporter with an essential leucine zipper motif [4].
• Our data suggests that zinc tolerance in A. halleri involves an expanded copy number of an ancestral MTP1 gene, encoding functional proteins that mediate the detoxification of zinc in the cell vacuole [5].
• Taken together, these data are consistent with MTP1 functioning to enhance plasma membrane Zn efflux, acting to confer Zn resistance independent of the vacuole in S. cerevisiae [6].
• In contrast, a third MTP1 gene in the genome of A. halleri generates only minor amounts of MTP1 transcripts and does not co-segregate with zinc tolerance [5].
• The availability of ZAT can lead to a better understanding of the mechanism of Zn homeostasis and resistance in plants [1].

Anatomical context of ZAT

• Xenopus laevis oocytes expressing AtMTP1 accumulate more Zn than oocytes expressing the AtMTP1(D94A) mutant or water-injected oocytes [2].
• Thus we propose that AtMTP1 is localized in the vacuolar membrane and is involved in sequestration of excess Zn in the cytoplasm into vacuoles to maintain Zn homeostasis [7].
• Zinc transporter of Arabidopsis thaliana AtMTP1 is localized to vacuolar membranes and implicated in zinc homeostasis [7].
• When AtMTP1 fused with green fluorescent protein was transiently expressed in protoplasts prepared from Arabidopsis suspension-cultured cells, green fluorescence was clearly observed in the vacuolar membrane [7].

Associations of ZAT with chemical compounds

• ZAT1p did not transport cobalt, and transported cadmium at only 1% of the zinc transport rate [3].
• AtMTP1 was immunochemically detected as a 43 kDa protein in the vacuolar membrane fractioned by sucrose density gradient centrifugation [7].
• We prepared a mutant AtMTP1 that lacked the major part (32 residues from 185 to 216) of a long histidine-rich hydrophilic loop in the central part of AtMTP1 [8].

References