Coupling of Protons and Potassium Gradients in Yeast

Ramos, Sofı́a; Peña, Pilar de la; Valle, Eulalia; Bergillos, Lourdes; Parra, Francisco; Lazo, Pedros S.

doi:10.1016/b978-0-12-428580-4.50040-x

Cited by 11 publications

(7 citation statements)

References 12 publications

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“…It was also inhibited by 2 mM DNP, indicating that K+ uptake depended on the existence of a transmembrane H' gradient. K + also stimulated H' efflux, producing half-maximum stimulation a t 312.5 pM (data not shown), which compares to aK, value for K' uptake by yeast of approximately 500 KM (Armstrong and Rothstein, 1967) and is consistent with its being a component of the coupled H'/K' fluxes (Pena, 1975;Borst-Pauwels, 1981;Ramos et. al., 1985)…”

Section: Energy-dependence Of H+ and K T Transportsupporting

confidence: 73%

“…These gradients are generally considered to directly energize uptake of a variety of solutes including certain sugars (Eddy, 1982) basic amino acids (Cooper, 1982), and divalent cations (Borst-Pauwels, 1981;Okorokov, 1985). H+ and K+ transport, and thus the potential energy represented by their concentration gradients, are considered to be coupled (Pena, 1975;Ramos et al, 1985). Consequently, the K+ gradient across the cell membrane represents a store of metabolic energy available for transport of solutes.…”

Section: Introductionmentioning

confidence: 99%

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Inhibition of H⁺ efflux and K⁺ uptake, and induction of K⁺ efflux in yeast by heavy metals

White

Gadd

1987

Environ. Toxicol. Water Qual.

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Energy and cell membrane ATPase-dependent H ' efflux from yeast cells was inhibited by heavy metals, which also inhibited energy-dependent K' uptake by the cells. Heavy metals also induced K' efflux from metabolizing cells in two phases: reversibly a t low concentrations and irreversibly at high concentratioas.The concentration dependence of all of these effects varied considerably between metals.The effect of in uiuo inhibition of H ' transporting ATPases on cell membrane polarization and thus on cellular transport processes, including heavy metal uptake, are discussed. It is proposed that the inhibition of H' efflux and the appearance of irreversible K' emux in yeast are potentially useful indicators of heavy metal toxicity toward yeast and possibly other fungi.

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Section: Energy-dependence Of H+ and K T Transportsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Inhibition of H⁺ efflux and K⁺ uptake, and induction of K⁺ efflux in yeast by heavy metals

White

Gadd

1987

Environ. Toxicol. Water Qual.

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“…Moreover, thiamin had no effect on the rate of Ph3MeP+ uptake in glucose-grown cells (not shown). These data, together with the fact that CCCP reduced the accumulated Ph3MeP+ by 90% in ethanol-grown cells [17], and that mitochondria1 inhibitors do not affect Ph3MeP+ uptake [17], led us to conclude that Ph3MeP+ can be used as a probe for A I~ in yeast, under our experimental conditions. However we cannot rule out the contribution of surface potential [19] to potentiate the observed Ph3MeP' uptake.…”

Section: Discussionmentioning

confidence: 58%

“…Although the validity of lipophilic cations to determine membrane potential quantitatively has been questionated in yeast, it is generally accepted that its accummulation in yeast, is a function of d y [8,[14][15][16][17][18][19]. Boxman et al [I41 have shown that the lipophilic cation Ph4P+ binds to several yeast constituents which invalidate this compound for quantitative determination of the membrane potential without correction for unspecific binding.…”

Section: Discussionmentioning

confidence: 99%

Trehalase activation in yeasts is mediated by an internal acidification

et al. 1986

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It has been reported that the addition of glucose, uncouplers and nystatin to yeast cells grown in a sugarfree medium causes trehalase activation; it has been postulated that this activation might be mediated by the depolarization of the plasma membrane. In this article the values of membrane potential and pH gradient across the plasma membrane of Saccharomyces cerevisiae have been determined under the same conditions as those in which trehalase is activated. Membrane potential was evaluated from the distribution of triphenylmethylphosphonium, the pH gradient from the distribution of benzoic acid across the plasma membrane. When the effect of several agents on the two components of the electrochemical proton gradient across the plasma membrane of ethanol-grown yeast cells were studied, under trehalase activation conditions, the following observations were made. (a) The addition of glucose activated trehalase and caused internal acidification of the cells, but had practically no effect on the membrane potential. (b) The addition of 200 mM KCI depolarized the cell membrane but did not affect the internal pH, nor trehalase activity. (c) Although carbonyl cyanide mchlorophenylhydrazone depolarized the cells at external pH 6.0 and 7.0, it only activated trehalase at an external pH 6.0, leading to the acidification of the internal medium at this pH. (d) Nystatin caused an increase in the triphenylmethylphosphonium accumulation at external pH 6.0 and 7.0, but only activated trehalase at external pH 6.0, causing acidification of the cell interior at this pH. (e) Activation of trehalase was also observed when the internal acidification was caused by addition of a weak acid such as acetate. It is concluded that trehalase activation is mediated by an intracellular acidification and is independent of the membrane potential.It has been established by several authors that glucose, proton conductors and nystatin cause trehalose breakdown [l], gluconeogenesis inhibition [2, 31 and glycolysis stimulation [4] in Succharomyces cerevisiae. The regulatory effects of these agents is believed to be mediated by an increase in the levels of intracellular CAMP which leads to an activation of the CAMP-dependent protein kinase. This enzyme causes the subsequent activation of trehalase and phosphofructo-2-kinase and the partial inactivation of fructose-l,6-bisphosphatase among other enzymes [l -41. It has been postulated that the increase in internal CAMP is caused by the depolarization of the plasma membrane, since glucose, uncouplers and nystatin produce rapid depolarization in Neurospora crama [5, 61. Although these agents elicited an increase of the CAMP levels in several yeast strains [2 -51, proof of a direct relationship between changes in membrane potential ( A y ) and fluctuations in CAMP concentrations in S. cerevisiue is still lacking. Proton conductors and nystatin [7] are known to cause an influx of protons which could affect both parameters of the electrochemical proton gradient. Therefore, the increase in internal CAMP leve...

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“…Since K+ uptake is coupled to H+ efflux (Peiia, 1975;Ramos et al, 1985), the K+-induced alkalinization of the cell interior could be due to the electrically coupled activities of the H+-ATPase and a K+ carrier. If so, this mechanism should be regulated differently in glucose-grown cells collected at the stationary phase from that in ethanol-grown cells, in which glucose-induced internal acidification persists even in the presence of 50 mM-K+ (Fig.…”

Section: Discussionmentioning

confidence: 99%

External K+ Affects the Internal Acidification Caused by the Addition of Glucose to Yeast Cells

Valle

Bergillos²,

Ramos³

1987

Microbiology

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In glucose-grown cells of Saccharomyces cerevisiae, collected during the stationary phase of growth, the addition of K+ to the external medium reversed glucose-induced internal acidification in 2 min. However, in ethanol-grown cells external K+ did not reverse the effect of glucose even after 20 min. The presence or absence of external K+ did not alter the modification of trehalase and fructose-1,6-bisphosphatase induced by glucose. It is concluded that transient acidification may be sufficient to cause the associated transient increase in cAMP.

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Coupling of Protons and Potassium Gradients in Yeast

Cited by 11 publications

References 12 publications

Inhibition of H⁺ efflux and K⁺ uptake, and induction of K⁺ efflux in yeast by heavy metals

Inhibition of H⁺ efflux and K⁺ uptake, and induction of K⁺ efflux in yeast by heavy metals

Trehalase activation in yeasts is mediated by an internal acidification

External K+ Affects the Internal Acidification Caused by the Addition of Glucose to Yeast Cells

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Coupling of Protons and Potassium Gradients in Yeast

Cited by 11 publications

References 12 publications

Inhibition of H+ efflux and K+ uptake, and induction of K+ efflux in yeast by heavy metals

Inhibition of H+ efflux and K+ uptake, and induction of K+ efflux in yeast by heavy metals

Trehalase activation in yeasts is mediated by an internal acidification

External K+ Affects the Internal Acidification Caused by the Addition of Glucose to Yeast Cells

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Inhibition of H⁺ efflux and K⁺ uptake, and induction of K⁺ efflux in yeast by heavy metals

Inhibition of H⁺ efflux and K⁺ uptake, and induction of K⁺ efflux in yeast by heavy metals