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Methionine-mediated lethality in yeast cells at elevated temperature
1Department of Microbiology and Molecular Genetics, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark 07103.
Abstract:
Saccharomyces cerevisiae cells grown at 30 degrees C in minimal medium containing methionine lose viability upon transfer to 45 degrees C, whereas cells grown in the absence of methionine survive. Cellular levels of two intermediates in the sulfate assimilation pathway, adenosine 5'-phosphosulfate (APS) and adenosine 5'-phosphosulfate 3'-phosphate, are increased by a posttranslational mechanism after sudden elevation of temperature in yeast cultures grown in the absence of methionine. Yeast cells unable to synthesize APS because of repression by methionine or mutation of the MET3 gene do not survive the temperature shift. Thus, methionine-mediated lethality at elevated temperature is linked to the inability to synthesize APS. The results demonstrate that APS plays an important role in thermotolerance.
Insights
Methionine causes yeast cells to lose viability at high temperatures. This lethality is linked to the inability to synthesize adenosine 5'-phosphosulfate (APS), a key molecule for thermotolerance.
Area of Science:
- * Molecular Biology
- * Cellular Stress Response
- * Biochemistry
Background:
- * Saccharomyces cerevisiae (baker's yeast) exhibits temperature-dependent viability.
- * Methionine's role in cellular stress, particularly at elevated temperatures, is not fully understood.
- * The sulfate assimilation pathway is crucial for cellular metabolism.
Purpose of the Study:
- * To investigate the mechanism of methionine-mediated lethality in yeast at high temperatures.
- * To determine the role of sulfate assimilation intermediates in yeast thermotolerance.
- * To elucidate the link between methionine, APS synthesis, and survival under heat stress.
Main Methods:
- * Comparative analysis of Saccharomyces cerevisiae viability under different growth conditions (presence/absence of methionine) and temperature shifts.
- * Measurement of intracellular levels of sulfate assimilation pathway intermediates, specifically adenosine 5"-phosphosulfate (APS) and adenosine 5"-phosphosulfate 3"-phosphate.
- * Genetic analysis involving yeast strains with repressed or mutated MET3 gene, affecting APS synthesis.
Main Results:
- * Yeast grown in methionine-containing media lost viability when shifted to 45°C, while those grown without methionine survived.
- * Elevated temperatures induced a posttranslational increase in APS and adenosine 5"-phosphosulfate 3"-phosphate levels in methionine-absent cultures.
- * Yeast strains unable to synthesize APS (due to methionine repression or MET3 mutation) did not survive the temperature increase.
Conclusions:
- * Methionine-mediated lethality at elevated temperatures in Saccharomyces cerevisiae is directly associated with impaired APS synthesis.
- * Adenosine 5"-phosphosulfate (APS) plays a critical role in yeast thermotolerance.
- * The sulfate assimilation pathway is a significant factor in cellular adaptation to heat stress.