Modulation of the Na,K-ATPase by Magnesium Ions

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APELL, Hans-Jürgen, Tanja HITZLER, Grischa SCHREIBER, 2017. Modulation of the Na,K-ATPase by Magnesium Ions. In: Biochemistry. 56(7), pp. 1005-1016. ISSN 0006-2960. eISSN 1520-4995

@article{Apell2017-02-21Modul-37889, title={Modulation of the Na,K-ATPase by Magnesium Ions}, year={2017}, doi={10.1021/acs.biochem.6b01243}, number={7}, volume={56}, issn={0006-2960}, journal={Biochemistry}, pages={1005--1016}, author={Apell, Hans-Jürgen and Hitzler, Tanja and Schreiber, Grischa} }

Apell, Hans-Jürgen Modulation of the Na,K-ATPase by Magnesium Ions eng Schreiber, Grischa 2017-03-07T13:36:30Z Schreiber, Grischa 2017-03-07T13:36:30Z 2017-02-21 Since the beginning of investigations of the Na,K-ATPase, it has been well-known that Mg<sup>2+</sup> is an essential cofactor for activation of enzymatic ATP hydrolysis without being transported through the cell membrane. Moreover, experimental evidence has been collected through the years that shows that Mg<sup>2+</sup> ions have a regulatory effect on ion transport by interacting with the cytoplasmic side of the ion pump. Our experiments allowed us to reveal the underlying mechanism. Mg<sup>2+</sup> is able to bind to a site outside the membrane domain of the protein's α subunit, close to the entrance of the access channel to the ion-binding sites, thus modifying the local concentration of the ions in the electrolyte, of which Na<sup>+</sup>, K<sup>+</sup>, and H<sup>+</sup> are of physiological interest. The decrease in the concentration of these cations can be explained by electrostatic interaction and estimated by the Debye-Hückel theory. This effect provokes the observed apparent reduction of the binding affinity of the binding sites of the Na,K-ATPase in the presence of various Mg<sup>2+</sup> concentrations. The presence of the bound Mg<sup>2+</sup>, however, does not affect the reaction kinetics of the transport function of the ion pump. Therefore, stopped-flow experiments could be performed to gain the first insight into the Na<sup>+</sup> binding kinetics on the cytoplasmic side by Mg<sup>2+</sup> concentration jump experiments. Apell, Hans-Jürgen Hitzler, Tanja Hitzler, Tanja

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