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Mutations of Ser-23 of the α1 subunit of the rat Na+/K+-ATPase to negatively charged amino acid residues mimic the functional effect of PKC-mediated phosphorylation

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Vasilets,  Larisa A.
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;
Institute for Chemical Physics Research, Russian Academy of Sciences, 142432 Chernogolovka, Moscow region, Russia;

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Postina,  Rolf
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Kirichenko,  Svetlana N.
Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;
Institute for Chemical Physics Research, Russian Academy of Sciences, 142432 Chernogolovka, Moscow region, Russia;

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Citation

Vasilets, L. A., Postina, R., & Kirichenko, S. N. (1999). Mutations of Ser-23 of the α1 subunit of the rat Na+/K+-ATPase to negatively charged amino acid residues mimic the functional effect of PKC-mediated phosphorylation. FEBS Letters, 455(1-2), 8-12. doi:10.1016/S0014-5793(99)00851-0.


Cite as: https://hdl.handle.net/21.11116/0000-0007-1DB7-B
Abstract
The Na+/K+-ATPase is a target protein for protein kinase C (PKC). The PKC-mediated phosphorylation of the rat α1 subunit at Ser-23 results in the inhibition of its transport function. To understand the molecular basis of the inhibition by PKC, the Ser-23 in the rat α1 subunit has been replaced by negatively (Asp, Glu) or positively (Lys) charged, or uncharged (Gln, Ala) residues, and the mutants were expressed in Xenopus oocytes. Ouabain-specific 86Rb uptake and pump-generated current as well as sensitivity to ouabain and to external K+ have been investigated. When Ser-23 was replaced by the negatively charged residues, transport function was inhibited, and simultaneously synthesis of the α subunits was enhanced. In addition, if Ser-23 was substituted by Glu, the KI value for inhibition of transport by ouabain was drastically increased from 46.5 μM to 1.05 mM. The data suggest that insertion of a negative charge within the N-terminus of α subunit of the Na+/K+-ATPase due to phosphorylation of Ser-23 plays an important role in the PKC-mediated inhibition of transport function.