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Phosphate transport system in paracoccus denitrificans.
Journal of Bioenergetics and Biomembranes
|February 1, 1983
Summary
Phosphate (Pi) uptake in Paracoccus denitrificans occurs in two phases, with the first representing net transport. The study suggests Pi enters cells via proton symport, not a Pi/dicarboxylate antiporter.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Understanding inorganic phosphate (Pi) transport is crucial for cellular energy metabolism and function.
- Paracoccus denitrificans is a model organism for studying bacterial respiration and transport mechanisms.
Purpose of the Study:
- To elucidate the mechanism of inorganic phosphate (Pi) uptake in Paracoccus denitrificans.
- To identify the specific transporters and conditions involved in Pi assimilation.
Main Methods:
- Investigated Pi uptake kinetics in bacterial cells and spheroplasts.
- Utilized inhibitors of transport and metabolism, including DCCD, n-butylmalonate, SH reagents (PCMB, mersalyl), valinomycin, and FCCP.
- Examined the effect of ion gradients and protonophores on Pi transport and efflux.
Main Results:
- Pi uptake exhibited a biphasic pattern, with the initial phase reflecting net transport.
- DCCD inhibited the second phase, indicating Pi esterification limits uptake rate.
- Sulfhydryl reagents inhibited Pi uptake but not efflux, suggesting involvement of specific cysteine residues.
- Potassium ion gradients and proton symport appear to be involved in Pi uptake.
Conclusions:
- Inorganic phosphate (Pi) transport in Paracoccus denitrificans is primarily mediated by a proton symporter.
- The Pi/dicarboxylate antiporter is likely not involved in Pi uptake.
- Cellular Pi utilization rate significantly influences the observed uptake kinetics.