Resistance to cadmium ions and formation of a cadmium-binding complex in various wild-type yeasts.
The resistance to cadmium ions (Cd-resistance) and possible formation of cadmium-binding complexes were examined in eight different wild-type yeasts. Saccharomyces exiguus, Pichia farinosa, Torulaspora delbrueckii and Schizosaccharomyces octosporus exhibited partial Cd-resistance, as compared to the Cd-resistant strain 301N and the Cu-resistant but Cd-sensitive strain X2180-1B of Saccharomyces cerevisiae. Saccharomyces carlsbergensis, Pichia mogii, Zygosaccharomyces rouxii and Kluyveromyces lactis were all Cd-sensitive. The partially Cd-sensitive species, with the exception of S. exiguus, accumulated Cd2+ ions in the cytoplasmic fraction to varying extents. This fraction from S. octosporus included a Cd-binding complex that contained (gamma EC)nG peptides known as cadystins or phytochelatins, while P. farinosa and T. delbrueckii synthesized Cd-binding proteins that were similar to the Cd-metallothionein produced by S. cerevisiae 301N in terms of molecular weight and amino acid composition. These results suggest that such cytoplasmic molecules play a role in the Cd-tolerance of the above three species of yeast. S. exiguus retained most cadmium in the cell wall fraction and no Cd-binding complex was found in the cytoplasm, an indication of the important role of the cell wall in its Cd-tolerance. Different modes of binding of Cd2+ ions appear to be involved in the Cd-resistance of wild-type yeasts and fungi.
Inouhe
M
M
Department of Biology, Faculty of Science, Ehime University, Matsuyama, Japan.
Sumiyoshi
M
M
Tohoyama
H
H
Joho
M
M
D000596:Amino Acids / Q000032:analysis; D002104:Cadmium / Q000378:metabolism* / Q000494:pharmacology*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D004352:Drug Resistance, Microbial; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D005978:Glutathione; D017136:Ion Transport; D008667:Metalloproteins / Q000378:metabolism; D008668:Metallothionein / Q000378:metabolism; D054811:Phytochelatins; D010940:Plant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D015003:Yeasts / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*
D000596:Amino Acids; D002352:Carrier Proteins; D005656:Fungal Proteins; D008667:Metalloproteins; D010940:Plant Proteins; D002104:Cadmium; D008668:Metallothionein; D054811:Phytochelatins; D005978:Glutathione