title: Heavy metal tolerance in the fission yeast requires an ATP-binding cassette-type vacuolar membrane transporter.
abstract: In response to heavy metal stress, plants and certain fungi, such as the fission yeast Schizosaccharomyces pombe, synthesize small metal-binding peptides known as phytochelatins. We have identified a cadmium sensitive S. pombe mutant deficient in the accumulation of a sulfide-containing phytochelatin-cadmium complex, and have isolated the gene, designated hmt1, that complements this mutant. The deduced protein sequence of the hmt1 gene product shares sequence identity with the family of ABC (ATP-binding cassette)-type transport proteins which includes the mammalian P-glycoproteins and CFTR, suggesting that the encoded product is an integral membrane protein. Analysis of fractionated fission yeast cell components indicates that the HMT1 polypeptide is associated with the vacuolar membrane. Additionally, fission yeast strains harboring an hmt1-expressing multicopy plasmid exhibit enhanced metal tolerance along with a higher intracellular level of cadmium, implying a relationship between HMT1 mediated transport and compartmentalization of heavy metals. This suggests that tissue-specific overproduction of a functional hmt1 product in transgenic plants might be a means to alter the tissue localization of these elements, such as for sequestering heavy metals away from consumable parts of crop plants.
authors.affiliation: Plant Gene Expression Center, US Department of Agriculture, Albany, CA 94710.
authors.forename: D F
authors.initials: DF
authors.lastname: Ortiz
authors.forename: L
authors.initials: L
authors.lastname: Kreppel
authors.forename: D M
authors.initials: DM
authors.lastname: Speiser
authors.forename: G
authors.initials: G
authors.lastname: Scheel
authors.forename: G
authors.initials: G
authors.lastname: McDonald
authors.forename: D W
authors.initials: DW
authors.lastname: Ow
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002104:Cadmium / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics; D005800:Genes, Fungal; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008780:Methyltransferases; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011484:Protein-Arginine N-Methyltransferases; D012568:Schizosaccharomyces / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D004271:DNA, Fungal; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C489670:hmt1 protein, S pombe; D002104:Cadmium; D000255:Adenosine Triphosphate; D008780:Methyltransferases; C077013:PRMT2 protein, human; D011484:Protein-Arginine N-Methyltransferases