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Temperature-sensitive mutants of yeast exhibiting a rapid inhibition of protein synthesis
Abstract:
Certain temperature-sensitive (ts(-)) mutants of yeast which cannot be corrected by nutritional supplementation exhibited a rapid cessation of protein synthesis after a shift to the restrictive temperature. Genetic and biochemical tests permitted a division of these mutants into four classes. This division was based upon genetic complementation patterns among the mutants and an investigation of glucose incorporation into macromolecules and polyribosome content in the mutants after a shift to the restrictive temperature. A study of these parameters in the parent strain (ts(+)) in the presence of certain well-characterized inhibitors allowed a tentative identification of the biochemical defects in each of the four classes. The properties of the mutants in class IA were consistent with the hypothesis that they result from a defect in the initiation of polypeptide chains or in ribonucleic acid synthesis; mutants in class IB from a defect in the elongation of polypeptide chains; mutants in class IIA from a defect in energy metabolism; and mutants in class IIB from a lesion affecting membrane function.
Insights
Certain temperature-sensitive yeast mutants rapidly stop protein synthesis at restrictive temperatures. Genetic and biochemical analyses classified these mutants into four groups, suggesting defects in protein initiation, elongation, energy metabolism, or membrane function.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Temperature-sensitive (ts(-)) yeast mutants unable to correct via nutritional supplementation were studied.
- These mutants show a rapid halt in protein synthesis upon temperature shift to restrictive conditions.
Purpose of the Study:
- To genetically and biochemically classify ts(-) yeast mutants based on their protein synthesis defects.
- To tentatively identify the specific biochemical lesions responsible for these defects.
Main Methods:
- Genetic complementation tests were performed on the mutants.
- Biochemical analyses included glucose incorporation into macromolecules and polyribosome content.
- Comparison with parent strains (ts(+)) and known inhibitors.
Main Results:
- Mutants were divided into four distinct classes (IA, IB, IIA, IIB).
- Class IA mutants suggested defects in polypeptide chain initiation or RNA synthesis.
- Class IB mutants indicated issues with polypeptide chain elongation.
- Class IIA mutants pointed to energy metabolism defects.
- Class IIB mutants suggested membrane function lesions.
Conclusions:
- The study successfully classified temperature-sensitive yeast mutants affecting protein synthesis into four categories.
- These classifications provide insights into essential cellular processes like protein synthesis, energy metabolism, and membrane function in yeast.