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Reduced plasma membrane permeability in a multiple cross-resistant strain of Saccharomyces cerevisiae
Abstract:
Single nuclear gene inheritance was shown to be responsible for increased resistance to: eight diverse inhibitors of mitochondrial function (antimycin, carbonylcyanide-m-chlorophenylhydrazone, chloramphenicol, oligomycin, tetracycline, triethyltin bromide, triphenylmethylphosphonium bromide and triton-X-165); and an inhibitor of cytoplasmic protein synthesis (cycloheximide). Continuous monitoring of oxygen uptake during respiratory adaptation showed that anerobic pretreatment of resistant cells sensitized respiratory adaptation to chloramphenicol and antimycin. However, since a depression of mitochondrial function by catabolite repression did not result in sensitization to antimycin, alteration of the mitochondrial membrane does not appear to be responsible for resistance to mitochondrial inhibition. Alteration of cellular binding sites was not responsible for resistance since in vitro mitochondrial protein synthesis was sensitive to chloramphenicol and in vitro mitochondrial respiration was sensitive to oligomycin, carbonylcyanide-m-chlorophenylhydrazone, and antimycin. Autoradiography of an ethylacetate-ethanol extract of [14C]chloramphenicol-treated resistant cells indicated that resistance was not due to enzymatic modification of inhibitors. The maintenance of an antimycin-resistant respiration by protoplasts of resistant cells ruled out the involvement of the cell wall in cellular resistance. The reduced transport of [14C]chloramphenicol by resistant cells (1% of normal cells) indicated that a single nuclear gene mutation can alter the permeability of the plasma membrane to many diverse inhibitors.
Insights
A single nuclear gene mutation confers resistance to diverse mitochondrial inhibitors by altering plasma membrane permeability. This mutation reduces the transport of inhibitors into resistant cells, impacting cellular function.
Area of Science:
- Cell Biology
- Genetics
- Biochemistry
Background:
- Mitochondrial function is crucial for cellular energy production.
- Resistance to mitochondrial inhibitors can arise from various genetic and biochemical mechanisms.
- Understanding these mechanisms is key to developing targeted therapies and understanding cellular defense.
Purpose of the Study:
- To investigate the genetic basis of cellular resistance to multiple mitochondrial inhibitors.
- To elucidate the mechanism by which this resistance is conferred.
- To determine if a single gene mutation can impact cellular permeability to diverse inhibitors.
Main Methods:
- Testing resistance to eight mitochondrial inhibitors and one cytoplasmic protein synthesis inhibitor.
- Monitoring oxygen uptake during respiratory adaptation.
- Assessing in vitro mitochondrial protein synthesis and respiration.
- Utilizing autoradiography to detect inhibitor modification.
- Employing protoplast assays to evaluate cell wall involvement.
- Measuring the transport of radiolabeled chloramphenicol.
Main Results:
- A single nuclear gene mutation conferred resistance to diverse mitochondrial and cytoplasmic inhibitors.
- Resistance was not due to altered mitochondrial membranes, binding sites, enzymatic modification, or cell wall involvement.
- Resistant cells exhibited significantly reduced transport of chloramphenicol (1% of normal cells).
- Anaerobic pretreatment sensitized resistant cells to certain inhibitors, but catabolite repression did not.
Conclusions:
- A single nuclear gene mutation is responsible for broad-spectrum inhibitor resistance.
- The primary mechanism involves altered plasma membrane permeability, reducing inhibitor uptake.
- This finding highlights the role of membrane transport in cellular defense against toxic compounds.