title: Predicted alterations in tertiary structure of the N-terminus of Na(+)/K(+)-ATPase alpha-subunit caused by phosphorylation or acidic replacement of the PKC phosphorylation site Ser-23.
abstract: The protein kinase C (PKC)-mediated phosphorylation of the Na(+)/K(+)-ATPase alpha-subunit has been shown to play an important role in regulation of the Na(+)/K(+)-ATPase activity. In the rat alpha1-subunit, phosphorylation occurs at Ser-23 and results in inhibition of the transport function of the Na(+)/K(+)-ATPase, which is mimicked by replacing the Ser-23 by the negatively charged glutamic acid or by aspartic acid. Using comparative molecular modeling, we investigated whether phosphorylation or acidic replacement at position 23 causes a dramatic change in the molecular electrostatic potential at position 23 as a result of insertion of a negative charge of the phosphoryl group or Glu per se, or whether, alternatively, the modification causes larger-scale conformational changes in the N-terminus of the alpha-subunit. The results predict a considerable conformational change of the 30-residue stretch around Ser-23 when mutated to the residues carrying a net negative charge or being phosphorylated. The structural rearrangements occur within the N-terminal helix-loop-helix motif with a set of charged residues. This motif has structural homology with one in the Ca(2+)-ATPase and may form a function-related structural site in the P-type ATPases. Comparative molecular modeling indicates a lengthening of the interhelical loop and an order-to-disorder transition by disrupting a helix at position 23 because of posphorylation.
authors.affiliation: Leibniz-Institute for Plant Biochemistry, Weinberg 3, D-06120 Halle/Salle, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Brandt
authors.forename: Alexander
authors.initials: A
authors.lastname: Anders
authors.forename: Larisa A
authors.initials: LA
authors.lastname: Vasilets
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000235:genetics; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D051381:Rats; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D012694:Serine; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase