Structural basis for species-specific differences in the phosphorylation of Na,K-ATPase by protein kinase C.
There is considerable evidence that protein kinases play a role in regulation of the activity of the Na,K-ATPase, but the characteristics of direct kinase phosphorylation of Na,K-ATPase subunits are still not well understood. There are 36 sites that could qualify as protein kinase C motifs in rat alpha 1. Here we have used protein fragmentation with trypsin to localize the site of phosphorylation of the rat Na,K-ATPase alpha 1 subunit to within the first 32 amino acids of the N terminus and then used direct sequencing of the phosphorylated protein to determine which of two candidate serine residues was modified. The result was that at most 25% of the 32P was found on Ser-11, a site that is well conserved in Na,K-ATPase alpha 1 subunits. The remaining 75% or more of the 32P was found on Ser-18, a site that is absent in many Na,K-ATPase alpha subunit sequences. This accounts for the observation that dog and pig alpha 1 subunits can be phosphorylated by protein kinase C only to much lower levels than can rat alpha 1. It is also likely to be relevant to other known species-specific effects of protein kinase C on Na,K-ATPase.
Feschenko
M S
MS
Laboratory of Membrane Biology, Massachusetts General Hospital, Charlestown 02129, USA.
Sweadner
K J
KJ
D000595:Amino Acid Sequence; D000818:Animals; D004285:Dogs; D006801:Humans; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013045:Species Specificity; D013552:Swine
D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase