The competition transport of sodium ions and protons in the cytoplasmic access channel of the Na+,K+-ATPase

Shcherbakov, A. A.; Apell, Jennifer N.; Соколов, В. С.

doi:10.1134/s1990747813020074

Cited by 3 publications

(16 citation statements)

References 29 publications

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“…Measurements of the capacitance increments at alternating voltage fre quencies between 2 and 200 Hz showed that the capacitance changes did not depend on the frequency (data not shown). This fact allows us to suppose that the exchange of ions between the solution and the binding sites at the cytoplasmic side of the Na + ,K + ATРase is sufficiently fast (in contrast to the transport of sodium ions at the extracellular side, studied earlier [19]). Taking this finding into account, we further per formed measurements at 64 Hz and assumed that at this frequency the ion distribution between solution and the binding sites is in equilibrium.…”

Section: Studies Of the Competitive Binding Of Sodium Ions And Protonsmentioning

confidence: 99%

“…The results were analyzed quantitatively with the help of the model described in [19]. This model is a generalization of the model of electrogenic transport of ions in the cytoplasmic access channel of the Na + ,K + ATPase developed earlier [13].…”

Section: Studies Of the Competitive Binding Of Sodium Ions And Protonsmentioning

confidence: 99%

“…The effect of sodium ions on these increments was determined as a difference of the increments measured at a fixed concentration of 10 mM and zero NaCl [19]. In the present study, to determine the binding constant of Na + and K + , exper iments were carried out at a constant applied fre quency (64 Hz) along with a gradual increase of the ion concentration in the solution.…”

Section: Studies Of the Competitive Binding Of Sodium Ions And Protonsmentioning

confidence: 99%

“…The observed small increments of the capacitance of the membrane with Na + ,K + ATPase were triggered by a fast decrease of pH due to photo lysis of caged H + [19]. The dependence of this signal on pH at various sodium concentrations allowed the determination of the pK values of the binding sites.…”

Section: Introductionmentioning

confidence: 99%

“…The capacitance and conductance increments induced by the photolysis of caged H + were measured by the technique described in [19]. The suspension of the membrane fragments with Na + ,K + ATPase (in a concentration of 20 μg/mL) and caged H + (300 μM) were added into the distal (with respect to the light source) compartment of the cell.…”

Section: Introductionmentioning

confidence: 99%

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Electrogenic binding of ions at the cytoplasmic side of the Na+,K+-ATPase

Tashkin

Gavril’chik

Ilovaisky

et al. 2015

Biochem. Moscow Suppl. Ser. A

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Abstract-Electrogenic binding of ions from the cytoplasmic side of the Na + ,K + ATPase has been studied by measurements of changes of the membrane capacitance and conductance triggered by a jump of pH or of the sodium ion concentration in the absence of ATP. The pH jumps were performed in experiments with membrane fragments containing purified Na + ,K + ATPase adsorbed to a bilayer lipid membrane (BLM). Protons were released in a sub millisecond time range from a photosensitive compound (caged H + ) triggered by a UV light flash. The sodium concentration jumps were carried out by a fast solution exchange in experi ments with membrane fragments attached to a solid supported membrane deposited on a gold electrode. The change of the membrane capacitance triggered by the pH jump depended on the sodium ion concentration. Potassium ions had a similar effect on the capacitance change triggered by a pH jump. The effects of these ions are explained by the their competition with protons in the binding sites on cytoplasmic side of the Na + ,K + ATPase. The approximation of the experimental data by a theoretical model yields the dissociation constants, K, and the cooperativity coefficients, n, of the binding sites for sodium ions (K = 2.7 mM, n = 2) and potassium ions (K = 1.7 mM, n = 2). In the presence of magnesium ions the apparent dissociation constants of sodium increased. A possible reason of the inhibition of sodium ion binding by magnesium ions can be an elec trostatic or conformational effect of magnesium ions bound to a separate site of the Na + ,K + ATPase close to the entrance to the sodium ion binding sites.

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Section: Studies Of the Competitive Binding Of Sodium Ions And Protonsmentioning

confidence: 99%

Section: Studies Of the Competitive Binding Of Sodium Ions And Protonsmentioning

confidence: 99%

Section: Studies Of the Competitive Binding Of Sodium Ions And Protonsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Electrogenic binding of ions at the cytoplasmic side of the Na+,K+-ATPase

Tashkin

Gavril’chik

Ilovaisky

et al. 2015

Biochem. Moscow Suppl. Ser. A

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Binding of Potassium Ions Inside the Access Channel at the Cytoplasmic Side of Na+,K+-ATPase

Vishnyakova

Tashkin

Terentjev

et al. 2018

Biochem. Moscow Suppl. Ser. A

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Binding of potassium ions through an access channel from the cytoplasmic side of Na + ,K +-ATPase and the effect of pH and magnesium ions on this process have been studied. The studies were carried out by a previously developed method of measuring small increments of the admittance (capacitance and conductivity) of a compound membrane consisting of a bilayer lipid membrane with adsorbed membranes fragments containing Na + ,K +-ATPase. The capacitance change of the membrane with the Na + ,K +-ATPase was induced abruptly by release of protons from a bound form (caged H +) upon a UV-light flash in the absence of magnesium ions. The change of admittance consisted of an initial fast jump and a slow relaxation to a stationary value within a time of about 1-2 s. The kinetics of the capacitance relaxation depended on pH and the concentration of magnesium and potassium ions. The dependence of the rapid capacitance jump on the potassium concentration corresponded to the predictions of the model developed earlier that describes binding of sodium or potassium ions in competition with protons. The effect of magnesium ions can be explained by the assuming that they bind to the Na + ,K +-ATPase and affect binding of potassium ions because of either changes in protein conformation or the creation of an electrostatic field in the access channel on the cytoplasmic side.

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Electrostatic Potentials Caused by the Release of Protons from Photoactivated Compound Sodium 2-Methoxy-5-nitrophenyl Sulfate at the Surface of Bilayer Lipid Membrane

Sokolov,

Tashkin,

Zykova

et al. 2023

Membranes

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Lateral transport and release of protons at the water–membrane interface play crucial roles in cell bioenergetics. Therefore, versatile techniques need to be developed for investigating as well as clarifying the main features of these processes at the molecular level. Here, we experimentally measured the kinetics of binding of protons released from the photoactivated compound sodium 2-methoxy-5-nitrophenyl sulfate (MNPS) at the surface of a bilayer lipid membrane (BLM). We developed a theoretical model of this process describing the damage of MNPS coupled with the release of the protons at the membrane surface, as well as the exchange of MNPS molecules and protons between the membrane and solution. We found that the total change in the boundary potential difference across the membrane, ∆ϕb, is the sum of opposing effects of adsorption of MNPS anions and release of protons at the membrane–water interface. Steady-state change in the ∆ϕb due to protons decreased with the concentration of the buffer and increased with the pH of the solution. The change in the concentration of protons evaluated from measurements of ∆ϕb was close to that in the unstirred water layer near the BLM. This result, as well as rate constants of the proton exchange between the membrane and the bulk solution, indicated that the rate-limiting step of the proton surface to bulk release is the change in the concentration of protons in the unstirred layer. This means that the protons released from MNPS remain in equilibrium between the BLM surface and an adjacent water layer.

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The competition transport of sodium ions and protons in the cytoplasmic access channel of the Na+,K+-ATPase

Cited by 3 publications

References 29 publications

Electrogenic binding of ions at the cytoplasmic side of the Na+,K+-ATPase

Electrogenic binding of ions at the cytoplasmic side of the Na+,K+-ATPase

Binding of Potassium Ions Inside the Access Channel at the Cytoplasmic Side of Na+,K+-ATPase

Electrostatic Potentials Caused by the Release of Protons from Photoactivated Compound Sodium 2-Methoxy-5-nitrophenyl Sulfate at the Surface of Bilayer Lipid Membrane

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