A potassium-dependent citric acid transport system in Aerobacter aerogenes

Eagon, R. G.; Wilkerson, L. S.

doi:10.1016/0006-291x(72)90074-5

Cited by 36 publications

(16 citation statements)

References 11 publications

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“…Similarities are also visible when considering the influence of pH on the Michaelis rate equation in classical enzymology [31]. Since increasing evidence is accumulating for the involvement of protons [32,33] or potassium ions [34] in transport systems, the ion-substrate symport hypothesis may not appear so unrealistic. It would further offer the possibility of interpreting coupling between energy and transport within the very general frame of the chemiosmotic theory proposed by Mitchell [30,35,36].…”

Section: Resultsmentioning

confidence: 90%

The Energy‐Coupling Controlled Efflux of 2‐Keto‐3‐deoxy‐d‐gluconate in Escherichia coli K 12

Lagarde¹,

Stoeber²

1975

European Journal of Biochemistry

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Experiments were devised to test the plausibility and the predictions of an efflux rate equation which was previously derived [lo].1. 2-Keto-3-deoxy-~-gluconate transport system conforms with universal laws relating zero-trans influx, influx at steady-state, steady-state levels of accumulation to external and internal substrate concentrations.2. Full-time-course uptake kinetics fit the linearized graphical representation that can be inferred from the integrated rate equation.3. Influx does not depend upon internal substrate concentration nor upon energy-coupling. 4.Zero-trans outflux (leak into empty medium) is a first-order process (rate constant: 0.02 min-l) and not mediated by the carrier. Absence of cis-competition with D-glucuronate is in agreement with a simple diffusion mechanism.5. Outflux increases when external substrate concentration is raised (counterflow). Outflux at steady-state equilibrates influx, and is a first-order process (rate constant: 0.15 min-I).6. Uncoupling with azide leads to accelerate zero-trans outflux by a factor of 2-3. No further acceleration is obtained when other classical uncouplers are used. The process remains first-order, independent of the amount of carrier, and is accelerated by the presence of internal D-glucuronate as a result from trans-inhibition of the recapture.7. Exchange outflux is all the more accelerated by azide as the carrier is less saturated. The process is clearly carrier-mediated and the outflux rate obeys a Michaelis law with respect to internal concentration. V is equal to V for influx.8. Homo and hetero-overshoot experiments are in agreement with the participation of the carrier for mediating influx as well as outflux.9. The kinetics of D-glucuronate outflux in a strain lacking the specific hexuronate permease but carrying the 2-keto-3-deoxy-~-gluconate permease are similar to those obtained with 2-keto-3-deoxy-D-gluconate.We draw the conclusion that energy-coupling promotes the adjustment of outflux without interfering with influx rate. It apparently acts by reducing, in a continuous range, the affinity of the carrier facing inwards. The discussion is focused on the comparison with previously published models and on possible molecular mechanisms.In previous papers we have shown that 2-ketoconcentration of 2-keto-3-deoxy-~-gluconate, we in-3-deoxy-~-gluconate could be actively transported tended to explore the influence of energy-coupling into Escherichia coli cells [l] as well as into membrane on the exit step. Though it is clear that influx is a vesicles [2] provided that the system responsible for carrier-mediated process exhibiting characteristic uptake is derepressed by specific mutations [3].Michaelian properties [l, 21, there may be multiple In order to reach a better understanding of the channels for outflux and the kinetic distinction between molecular mechanisms leading to the intracellular them is often difficult [4,5]. However, a widespread Eur. J. Biochem. 55 (1975)

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Section: Resultsmentioning

confidence: 90%

The Energy‐Coupling Controlled Efflux of 2‐Keto‐3‐deoxy‐d‐gluconate in Escherichia coli K 12

Lagarde¹,

Stoeber²

1975

European Journal of Biochemistry

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“…Based on these observations, it appeared that lactate efflux created a ApH that subsequently drove malate uptake. Proton symport mechanisms for malate transport have also been observed in Saccharomyces cerevisiae, E. coli, and Klebsiella aerogenes (6,13,17).…”

Section: Discussionmentioning

confidence: 93%

“…Malate transport could be driven by a ZApH, but it appeared that the stoichiometry of malateproton symport was variable. At low malate concentrations, malate transport and lactate efflux constituted an electroneu-washed cell suspensions were incubated at 30°C for 0 to 2 h. The fermentation was terminated by centrifugation (1.5 ml, 13,000 x g, 1 min, 23°C), and the supernatant was analyzed for L-malic acid.…”

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confidence: 99%

Electrogenic L-malate transport by Lactobacillus plantarum: a basis for energy derivation from malolactic fermentation

1991

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L-Malate transport in Lactobacillus plantarum was inducible, and the pH optimum was 4.5. Malate uptake could be driven by an artificial proton gradient (ApH) or an electroneutral lactate efflux. Because L-lactate efflux was unable to drive L-malate transport in the absence of a ApH, it did not appear that the carrier was a malate-lactate exchanger. The kinetics of malate transport were, however, biphasic, suggesting that the external malate concentration was also serving as a driving force for low-affinity malate uptake. Because the electrical potential (At, inside negative) inhibited malate transport, it appeared that the malate transportlactate efflux couple was electrogenic (net negative) at high concentrations of malate. De-energized cells that were provided with malate only generated a large proton motive force (>100 mV) when the malate concentration was greater than 5 mM, and malate only caused an increase in cell yield (glucose-limited chemostats) when malate accumulated in the culture vessel. The use of the malate gradient to drive malate transport (facilitated diffusion) explains how L. plantarum derives energy from malolactic fermentation, a process which does not involve substrate-level phosphorylation.

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“…Active transport of various substrates is dependent on a sufficient intracellular concentration of potassium. These potassium-dependent uptake systems include amino acid transport (glutamate, alanine, aspartate) in Staphylococcus aureus [50], fl-galactoside transport in E. coli [51], amino acid and sugar uptake in S. faecalis [52], and citric acid uptake in Aerobacter aerogenes [53]. In addition, phosphate uptake and potassium accumulation are found to be interdependent in E. coli [54].…”

Section: Accumulation Of Potassiummentioning

confidence: 99%

Osmoregulation and compatible solutes in eubacteria

Imhoff¹

1986

FEMS Microbiology Letters

153

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Osmotic adaption by halophilic and halotolerant bacteria is generally achieved by the accumulation or synthesis of several organic solutes. Accumulation by uptake from the medium is preferred over biosynthesis. The chemical nature of the major solute is important in determining the degree of osmotolerance of the organism. Glycine betaine accumulation confers a greater degree of osmotolerance than proline, which in turn confers more osmotolerance than glutamate accumulation. The occurrence and uptake of these solutes in a variety of eubacteria is reviewed.

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A potassium-dependent citric acid transport system in Aerobacter aerogenes

Cited by 36 publications

References 11 publications

The Energy‐Coupling Controlled Efflux of 2‐Keto‐3‐deoxy‐d‐gluconate in Escherichia coli K 12

The Energy‐Coupling Controlled Efflux of 2‐Keto‐3‐deoxy‐d‐gluconate in Escherichia coli K 12

Electrogenic L-malate transport by Lactobacillus plantarum: a basis for energy derivation from malolactic fermentation

Osmoregulation and compatible solutes in eubacteria

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