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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
Author(s) -
Vasilets Larisa A.,
Postina Rolf,
Kirichenko Svetla.
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00851-0
Subject(s) - ouabain , phosphorylation , xenopus , protein kinase c , protein subunit , chemistry , atpase , microbiology and biotechnology , biochemistry , biophysics , biology , enzyme , sodium , organic chemistry , gene
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 To understand the molecular basis of the inhibition by PKC, the Ser‐23 in the rat α1 subunit has been replaced by negatively (Asp, Glu) or positively (Lys) charged, or uncharged (Gln, Ala) residues, and the mutants were expressed in Xenopus oocytes.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 86 Rb 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 K I 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.