PMID:7042336

Citation	Meury, J and Kepes, A (1981) The regulation of potassium fluxes for the adjustment and maintenance of potassium levels in Escherichia coli. Eur. J. Biochem. 119:165-70
Abstract	The regulation of K+ fluxes has been studied in Escherichia coli after depletion of K+ by an osmotic shock or at steady state of potassium accumulation. In the absence of a carbon source, bacteria accumulate K+ to an intracellular level near 0.1 M about half of actively metabolizing cells. During uptake the rate of net unidirectional influx decreased with time down to zero as a plateau was reached and no efflux was observed. Accumulated K+ was not exchanged with external K+ under these conditions. In the presence of a carbon source bacteria took up potassium to an intracellular concentration near 0.2 M. Efflux was delayed: it started only when 50% of final cellular K+ has been taken up. At steady state cellular K+ was exchangeable with external K+. The removal of the carbon source or the addition of respiratory inhibitors immediately stopped the K+ influx but did not affect efflux until the cellular K+ concentration has dropped to a level near 0.1 M; residual potassium was no longer exchangeable with external potassium. Maintaining such an impermeability to K+ ion does not require energy (delta psi or ATP), even though residual K+ is concentrated 100-fold compared to K+ in the medium. These results suggest that K+ efflux is dependent on active metabolism and on the concentration of intracellular K+ above a threshold. Unidirectional influx is also regulated by intracellular K+ according to a different concentration dependence. It appears that the trkA system, which is the only functional system under these experimental conditions is not a 'pump and leak' type of transport system.
Links	PubMed
Keywords	Biological Transport; Carbon/pharmacology; Energy Metabolism/drug effects; Escherichia coli/metabolism; Osmotic Pressure; Potassium/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:TRKA	involved_in	GO:0006813: potassium ion transport	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete
ECOLI:TRKA	enables	GO:0008324: cation transmembrane transporter activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete

References

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