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Transport overshoot during 2-methyl-4-amino-5-hydroxymethylpyrimidine uptake by Saccharomyces cerevisiae
A Iwashima1, Y Kimura, Y Kawasaki
1Department of Biochemistry, Kyoto Prefectural University of Medicine, Japan.
Abstract:
The transport overshoot during 2-methyl-4-amino-5-hydroxymethylpyrimidine (hydroxymethylpyrimidine) uptake by the thiamin transport system in Saccharomyces cerevisiae was investigated. The overshoot was found to be temperature- and energy-dependent and affected by the growth phase of the yeast. The efflux system for hydroxymethylpyrimidine appeared to be more sensitive to 2,4-dinitrophenol than the influx system, resulting in the loss of the overshoot of the pyrimidine in the presence of the uncoupler. Furthermore, the overshoot did not occur after the preincubation of yeast cells with inhibitors of protein synthesis such as cycloheximide and anisomycin. These results suggest that an active efflux system for hydroxymethylpyrimidine, which is rapidly synthesized, is involved in the overshoot of this pyrimidine during its transport in S. cerevisiae.
Insights
Investigating Saccharomyces cerevisiae, this study reveals that an active efflux system drives hydroxymethylpyrimidine transport overshoot. This process is energy-dependent and sensitive to protein synthesis inhibitors.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Thiamin (vitamin B1) is essential for numerous metabolic processes.
- Understanding nutrient transport systems in yeast is crucial for biotechnology and cellular metabolism research.
- 2-methyl-4-amino-5-hydroxymethylpyrimidine (hydroxymethylpyrimidine) is a key precursor in thiamin biosynthesis.
Purpose of the Study:
- To investigate the mechanism of transport overshoot for hydroxymethylpyrimidine in Saccharomyces cerevisiae.
- To elucidate the role of influx and efflux systems in this phenomenon.
- To determine the energy and protein synthesis dependence of hydroxymethylpyrimidine transport.
Main Methods:
- Utilized Saccharomyces cerevisiae as a model organism.
- Investigated hydroxymethylpyrimidine uptake under varying temperature conditions.
- Assessed the impact of energy depletion (using 2,4-dinitrophenol) and protein synthesis inhibition (cycloheximide, anisomycin) on transport kinetics.
- Analyzed the influence of yeast growth phase on transport overshoot.
Main Results:
- Hydroxymethylpyrimidine transport overshoot is dependent on temperature and cellular energy levels.
- The efflux system for hydroxymethylpyrimidine is more sensitive to the uncoupler 2,4-dinitrophenol than the influx system.
- Inhibition of protein synthesis prevents the observed transport overshoot.
- Yeast growth phase significantly affects the magnitude of the overshoot phenomenon.
Conclusions:
- An active efflux system for rapidly synthesized hydroxymethylpyrimidine is implicated in the transport overshoot.
- The overshoot is a regulated process involving both influx and efflux mechanisms.
- Cellular energy status and ongoing protein synthesis are critical for maintaining the transport overshoot in S. cerevisiae.