Journal of Biological Chemistry
Volume 277, Issue 7, 15 February 2002, Pages 4738-4746
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MEMBRANE TRANSPORT STRUCTURE FUNCTION AND BIOGENESIS
GmZIP1 Encodes a Symbiosis-specific Zinc Transporter in Soybean*

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The importance of zinc in organisms is clearly established, and mechanisms involved in zinc acquisition by plants have recently received increased interest. In this report, the identification, characterization and location of GmZIP1, the first soybean member of the ZIP family of metal transporters, are described. GmZIP1 was found to possess eight putative transmembrane domains together with a histidine-rich extra-membrane loop. By functional complementation of zrt1zrt2 yeast cells no longer able to take up zinc, GmZIP1 was found to be highly selective for zinc, with an estimated K m value of 13.8 μm. Cadmium was the only other metal tested able to inhibit zinc uptake in yeast. An antibody raised against GmZIP1 specifically localized the protein to the peribacteroid membrane, an endosymbiotic membrane in nodules resulting from the interaction of the plant with its microsymbiont. The specific expression of GmZIP1 in nodules was confirmed by Northern blot, with no expression in roots, stems, or leaves of nodulated soybean plants. Antibodies to GmZIP1 inhibited zinc uptake by symbiosomes, indicating that at least some of the zinc uptake observed in isolated symbiosomes could be attributed to GmZIP1. The orientation of the protein in the membrane and its possible role in the symbiosis are discussed.

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Published, JBC Papers in Press, November 12, 2001, DOI 10.1074/jbc.M106754200

*

This research was supported by the Australian Research Council (to D. A. D.), the CNRS Programme International de Cooperation Scientifique Program 637 (to S. M., A. P.), and the Department of Energy Grant DE-FG07-97ER20292 (to M. L. G.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EBI Data Bank with accession number(s) .

§

Both authors contributed equally to this work.

Supported by an Australian Postgraduate Research Award.