INVESTIGADORES
GONZALEZ LEBRERO Rodolfo Martin
artículos
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/es:
RODOLFO M GONZÁLEZ-LEBRERO; SERGIO BENJAMÍN, KAUFMAN; PATRICIO J, GARRAHAN; ROLANDO CARLOS, ROSSI
Revista:
JOURNAL OF BIOLOGICAL CHEMISTRY
Referencias:
Año: 2002 vol. 277 p. 5922 - 5928
ISSN:
0021-9258
Resumen:
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.