Role of a Candida albicans P1-type ATPase in resistance to copper and silver ion toxicity.
Copper ion homeostasis is complicated in that copper is an essential element needed for a variety of cellular processes but is toxic at excess levels. To identify Candida albicans genes that are involved in resistance to copper ion toxicity, a library containing inserts of C. albicans genomic DNA was used to complement the copper sensitivity phenotype of a Saccharomyces cerevisiae cup1Delta strain that is unable to produce Cup1p, a metallothionein (MT) responsible for high-level copper ion resistance. A P1-type ATPase (CPx type) that is closely related to the human Menkes and Wilson disease proteins was cloned. The gene encoding this pump was termed CRD1 (for copper resistance determinant). A gene encoding a 76-amino-acid MT similar to higher eukaryotic MTs in structure was also cloned, and the gene was termed CRD2. Transcription of the CRD1 gene was found to increase upon growth with increasing copper levels, while the CRD2 mRNA was expressed at a constant level. Strains with the CRD1 gene disrupted were extremely sensitive to exogenous copper and failed to grow in medium containing 100 microM CuSO(4). These crd1 strains also exhibited increased sensitivity to silver and cadmium, indicating that Crd1p is somewhat promiscuous with respect to metal ion transport. Although strains with the CRD2 gene disrupted showed reduced growth rate with increasing copper concentration, the crd2 mutants eventually attained wild-type levels of growth, demonstrating that CRD2 is less important for resistance to copper ion toxicity. Crd1p is the first example of a eukaryotic copper pump that provides the primary source of cellular copper resistance, and its ability to confer silver resistance may enhance the prevalence of C. albicans as a nosocomial pathogen.
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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Riggle
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Kumamoto
D018528:ATP-Binding Cassette Transporters; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002176:Candida albicans / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D027682:Cation Transport Proteins; D003001:Cloning, Molecular; D003300:Copper / Q000494:pharmacology*; D019327:Copper Sulfate / Q000494:pharmacology; D000079922:Copper Transport Proteins; D003470:Culture Media; D004271:DNA, Fungal; D004352:Drug Resistance, Microbial; D005656:Fungal Proteins; D015870:Gene Expression; D005800:Genes, Fungal; D016681:Genome, Fungal; D006801:Humans; D007477:Ions; D008565:Membrane Proteins; D008668:Metallothionein / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D010641:Phenotype; D012441:Saccharomyces cerevisiae; D012834:Silver / Q000494:pharmacology*; D012835:Silver Nitrate / Q000494:pharmacology
D018528:ATP-Binding Cassette Transporters; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; C413336:Crd2 protein, Candida albicans; D003470:Culture Media; D004271:DNA, Fungal; D005656:Fungal Proteins; D007477:Ions; D008565:Membrane Proteins; D012834:Silver; D003300:Copper; D008668:Metallothionein; D012835:Silver Nitrate; D000251:Adenosine Triphosphatases; C413335:CRD1 protein, Candida albicans; D019327:Copper Sulfate