Balesaria S, Hogstrand C. Identification, cloning and characterization of a plasma membrane zinc efflux transporter, TrZnT-1, from fugu pufferfish (Takifugu rubripes).
Biochem J 2006;
394:485-93. [PMID:
16212555 PMCID:
PMC1408679 DOI:
10.1042/bj20050627]
[Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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).
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