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Abstract:

We used the direct route of occlusion to study the equilibrium between free and occluded Rb+ in the Na+/K+-ATPase, in media with different concentrations of ATP, Mg2+, or Na+. An empirical equation, with the restrictions imposed by the stoichiometry of ligand binding was fitted to the data. This allowed us to identify which states of the enzyme were present in each condition and to work out the schemes and equations that describe the equilibria between the ATPase, Rb+, and ATP, Mg2+, or Na+. These equations were fitted to the corresponding experimental data to find out the values of the equilibrium constants of the reactions connecting the different enzyme states. The three ligands decreased the apparent affinity for Rb+ occlusion without affecting the occlusion capacity. With [ATP] tending to infinity, enzyme species with one or two occluded Rb+ seem to be present and full occlusion seems to occur in enzymes saturated with the nucleotide. In contrast, when either [Mg2+] or [Na+] tended to infinity no occlusion was detectable. Both Mg2+ and Na+ are displaced by Rb+ through a process that seems to need the binding and occlusion of two Rb+, which suggests that in these conditions Rb+ occlusion regains the stoichiometry of the physiological operation of the Na+ pump.

Registro:

Documento: Artículo
Título:The occlusion of Rb+ in the Na+/K+-ATPase. II. The effects of Rb+, Na+, Mg2+, or ATP on the equilibrium between free and occluded Rb+
Autor:González-Lebrero, R.M.; Kaufman, S.B.; Garrahan, P.J.; Rossi, R.C.
Filiación:Inst. de Quimica y Fisicoquim. Biol., Departamento de Quimica Biologica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
Palabras clave:Magnesium printing plates; Physiology; Positive ions; Potassium; Rubidium; Sodium; Stoichiometry; Occlusion capacity; Enzymes; adenosine triphosphatase (potassium sodium); adenosine triphosphate; magnesium ion; nucleotide; rubidium ion; sodium ion; article; enzyme analysis; equilibrium constant; ligand binding; priority journal; stoichiometry; Adenosine Triphosphate; Animals; Kidney; Kinetics; Magnesium; Models, Theoretical; Na(+)-K(+)-Exchanging ATPase; Rubidium; Sodium; Swine
Año:2002
Volumen:277
Número:8
Página de inicio:5922
Página de fin:5928
DOI: http://dx.doi.org/10.1074/jbc.M105887200
Título revista:Journal of Biological Chemistry
Título revista abreviado:J. Biol. Chem.
ISSN:00219258
CODEN:JBCHA
CAS:Adenosine Triphosphate, 56-65-5; Magnesium, 7439-95-4; Na(+)-K(+)-Exchanging ATPase, EC 3.6.1.37; Rubidium, 7440-17-7; Sodium, 7440-23-5
Registro:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219258_v277_n8_p5922_GonzalezLebrero

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Citas:

---------- APA ----------
González-Lebrero, R.M., Kaufman, S.B., Garrahan, P.J. & Rossi, R.C. (2002) . The occlusion of Rb+ in the Na+/K+-ATPase. II. The effects of Rb+, Na+, Mg2+, or ATP on the equilibrium between free and occluded Rb+. Journal of Biological Chemistry, 277(8), 5922-5928.
http://dx.doi.org/10.1074/jbc.M105887200
---------- CHICAGO ----------
González-Lebrero, R.M., Kaufman, S.B., Garrahan, P.J., Rossi, R.C. "The occlusion of Rb+ in the Na+/K+-ATPase. II. The effects of Rb+, Na+, Mg2+, or ATP on the equilibrium between free and occluded Rb+" . Journal of Biological Chemistry 277, no. 8 (2002) : 5922-5928.
http://dx.doi.org/10.1074/jbc.M105887200
---------- MLA ----------
González-Lebrero, R.M., Kaufman, S.B., Garrahan, P.J., Rossi, R.C. "The occlusion of Rb+ in the Na+/K+-ATPase. II. The effects of Rb+, Na+, Mg2+, or ATP on the equilibrium between free and occluded Rb+" . Journal of Biological Chemistry, vol. 277, no. 8, 2002, pp. 5922-5928.
http://dx.doi.org/10.1074/jbc.M105887200
---------- VANCOUVER ----------
González-Lebrero, R.M., Kaufman, S.B., Garrahan, P.J., Rossi, R.C. The occlusion of Rb+ in the Na+/K+-ATPase. II. The effects of Rb+, Na+, Mg2+, or ATP on the equilibrium between free and occluded Rb+. J. Biol. Chem. 2002;277(8):5922-5928.
http://dx.doi.org/10.1074/jbc.M105887200