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Mutations in Saccharomyces cerevisiae which confer resistance to several amino acid analogs
1Department of Biology, Brandeis University, Waltham, Massachusetts 02254.
Abstract:
Four new complementation groups of mutations which confer resistance to several amino acid analogs in Saccharomyces cerevisiae are described. These mutants were isolated on medium containing urea as the nitrogen source, in contrast to previous studies that had used medium containing proline. All four resistance to amino acid analog (raa) complementation groups appear to confer resistance by reducing amino acid analog and amino acid uptake. In some genetic backgrounds, raa leu2 and raa thr4 double mutants are inviable, even on rich medium. The raa4 mutation may affect multiple amino acid transport systems, since raa4 mutants are unable to use proline as a nitrogen source. raa4 is, however, unlinked to a previously described amino acid analog resistance and proline uptake mutant, aap1, or to the general amino acid permease mutant gap1. Both raa4 and gap1 prevent uptake of [3H]leucine in liquid cultures. The raa1, raa2, and raa3 mutants affect only a subset of the amino acid analogs and amino acids affected by raa4. The phenotypes of raa1, -2, and -3 mutants are readily observed on agar plates but are not seen in uptake and incorporation of amino acids measured in liquid media.
Insights
Four new yeast mutants resistant to amino acid analogs were identified by reducing nutrient uptake. Some double mutants showed inviability, suggesting essential transport functions are affected.
Area of Science:
- Genetics
- Molecular Biology
- Biochemistry
Background:
- Amino acid analogs are used to study nutrient transport in Saccharomyces cerevisiae.
- Previous studies primarily utilized proline-containing media for mutant isolation.
Purpose of the Study:
- To identify and characterize new mutations conferring resistance to amino acid analogs in yeast.
- To investigate the mechanisms underlying this resistance, focusing on nutrient uptake.
Main Methods:
- Isolation of yeast mutants resistant to amino acid analogs on urea-containing medium.
- Complementation analysis to establish new resistance (raa) groups.
- Assessment of amino acid and analog uptake in wild-type and mutant strains.
- Genetic crosses to analyze double mutant phenotypes and linkage.
Main Results:
- Four new complementation groups (raa1-raa4) conferring resistance to amino acid analogs were identified.
- All identified raa mutants exhibit reduced uptake of amino acid analogs and amino acids.
- The raa4 mutation impacts multiple amino acid transport systems, affecting proline utilization.
- raa4 and gap1 mutants similarly inhibit [3H]leucine uptake, while raa1-3 affect a subset of analogs.
Conclusions:
- New yeast mutations affecting amino acid transport have been characterized.
- Reduced nutrient uptake is a common mechanism for amino acid analog resistance in these mutants.
- The raa4 mutation represents a significant disruption of amino acid transport pathways in yeast.