title: Identification, cloning and characterization of a plasma membrane zinc efflux transporter, TrZnT-1, from fugu pufferfish (Takifugu rubripes).
abstract: An orthologue of the mammalian ZnT-1 (zinc transporter-1) gene was cloned from the intestine of the torafugu pufferfish (Takifugu rubripes), demonstrating that this gene predates the evolution of land-living vertebrates. TrZnT-1 (T. rubripes ZnT-1) shares overall topology with other members of the ZnT-1 family of zinc transporters, with six TMs (transmembrane domains) including a large histidine-rich intracellular loop between TM IV and V and intracellular C- and N-termini. Expression of TrZnT-1 in a metallothionein acquiescent cell line suggested that this protein reduces intracellular Zn2+ levels. Manipulation of the transporting media showed that several externally applied hydrominerals had no effect on TrZnT-1 activity. However, addition of N-ethylmaleimide increased TrZnT-1-mediated transport, possibly by increasing intracellular free Zn2+ levels by Zn2+ release from carrier proteins. Generation of a specific antibody and subsequent immunocytochemistry on fixed cells overexpressing TrZnT-1 indicated that the protein is localized to the plasma membrane in these cells. The genomic organization of TrZnT-1 is the same as that in mammals with two exons. The upstream regulatory region of the TrZnT-1 gene contains several putative cis-acting elements, including metal-response elements and an Sp1 site. Analysis of the DNA contigs surrounding the TrZnT-1 gene reveal limited synteny between corresponding regions in the rat, mouse and human; however, this was very low, with only two syntenic genes, ZnT-1 and NEK2 (never in mitosis gene A-related kinase).
authors.affiliation: King's College London, Nutritional Sciences Research Division, Department of Biochemistry, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Sara
authors.initials: S
authors.lastname: Balesaria
authors.forename: Christer
authors.initials: C
authors.lastname: Hogstrand
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D023741:Takifugu / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; C017800:zinc-binding protein