The occlusion of Rb+ in the Na+/K+-ATPase. I. The identity of occluded states formed by the physiological or the direct routes: Occlusion/deocclusion kinetics through the direct route

Occlusion of K+ or its congeners in the Na+/K+-ATPase occurs after K+-dependent dephosphorylation (physiological route) or in media lacking ATP and Na+ (direct route). The effects of Pi or ATP on the kinetics of deocclusion of the K+-congener Rb+ formed by each of the above mentioned routes was inde...

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Detalles Bibliográficos
Autores principales: González-Lebrero, R.M., Kaufman, S.B., Montes, M.R., Nørby, J.G., Garrahan, P.J., Rossi, R.C.
Formato: JOUR
Materias:
Physiology
Positive ions
Potassium
Rate constants
Rubidium
Sodium
Congeners
Enzymes
adenosine triphosphatase (potassium sodium)
adenosine triphosphate
phosphate
potassium ion
rubidium ion
sodium ion
active transport
article
dephosphorylation
enzyme analysis
hydrolysis
nonhuman
priority journal
swine
Adenosine Triphosphate
Animals
Kidney
Kinetics
Models, Theoretical
Na(+)-K(+)-Exchanging ATPase
Phosphates
Regression Analysis
Swine
Sus scrofa
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00219258_v277_n8_p5910_GonzalezLebrero
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:Occlusion of K+ or its congeners in the Na+/K+-ATPase occurs after K+-dependent dephosphorylation (physiological route) or in media lacking ATP and Na+ (direct route). The effects of Pi or ATP on the kinetics of deocclusion of the K+-congener Rb+ formed by each of the above mentioned routes was independent of the route of occlusion, which suggests that both routes lead to the same enzyme intermediate. The time course of occlusion via the direct route can be described by the sum of two exponential functions plus a small component of very high velocity. At equilibrium, occluded Rb+ is a hyperbolic function of free [Rb+] suggesting that the direct route results in enzyme states holding either one or two occluded Rb+. Release of occluded Rb+ follows the sum of two decreasing exponential functions of time, corresponding to two phases with similar sizes. These phases are not caused by independent physical compartments. The rate constant of one of the phases is reduced up to 30 times by free Rb+. When Rb+ is the only pump ligand, the kinetics of occlusion and deocclusion through the direct route are consistent with an ordered-sequential process with additional independent step(s) interposed between the uptake or the release of each occluded Rb+.

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