Resistance of haploid yeast to hydrogen peroxide and to tert-butylhydroperoxide strongly increases when 4% glucose is replaced by glycerol or ethanol as the carbon source of the complex medium. Using a GSH1-promoter-lacZ-fusion reporter construct we could demonstrate that GSH1 is one of the genes that are up-regulated during the shift from fermentative to oxidative metabolism. A gsh1 mutant did not exhibit respiratory growth resistance to H2O2, whereas it was only slightly impaired in acquiring resistance against t-BOOH in the same experimental conditions. An isogenic deltayap1 mutant, although more sensitive to oxidative stress than the wild-type (WT), could increase resistance to both peroxides by a similar factor as observed for the WT when shifted from 4% glucose to a non-fermentable carbon source. This indicates that in this case induction of resistance to oxidative stress is independent from Yap1 and from the Yap1-mediated stress response via the STRE motif.
Two genes in Saccharomyces cerevisiae, ALR1 and ALR2, encode transmembrane proteins involved in Mg2+ uptake. The present study investigates the phylogenetic relationship of Alr1p/Alr2p with bacterial CorA proteins and some proteins related to Mg2+ influx/efflux transport in mitochondrial and bacterial zinc transporters; including hydrophobic cluster analysis (HCA). The phylogenetic results indicate that the Alrp sequences of S. cerevisiae share a common carboxy-terminus with proteins related to zinc efflux transport. We also analyse the intracellular metal content by particle-induced X-ray emission (PIXE) after cell exposure to cadmium. The PIXE analysis of cadmium-exposed ALR mutants and wild-type yeast cells suggests that Alrp has a central role in cell survival in a cadmium-rich environment.
One gene in Saccharomyces cerevisiae, ALR1, encodes a transmembrane protein involved in the transport of Mg 2+ into cells. Overexpression of this gene changes the tolerance of S. cerevisiae to several metal cations. In order to study the cellular uptake mechanism of metal cations in S. cerevisiae, an accurate determination of the metals present in the cells is needed. In this work, particle-induced x-ray emission (PIXE) was employed to analyze the intracellular metal content after cell exposure to cadmium. To that end, a specific method for sample preparation was developed. The samples were irradiated with a 2 MeV proton beam, while the induced x-rays were detected with a high-purity germanium detector. The PIXE results for cadmium-exposed ALR1 mutant and wild-type yeast cells suggest that Alr1p has a central role in the cell survival process in a cadmium-rich environment.
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