Characterization of a competitive and reversible ligand to E2 conformation of Na, K ATPase molecule
1Department of Medicine/Nephrology, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27103.
Abstract:
The binding of cardiac glycosides to the E2 conformation of Na, K ATPase suggests that this conformation may represent a potential regulatory site for an endogenous ligand. To examine this hypothesis, delipidated and desalted, ethanolic extracts were prepared from plasma. Plasma extracts produced displacement of 3H-ouabain from Type I and II high affinity binding sites that was parallel to the displacement by cold ouabain. Plasma extracts shifted the binding curve of 3H-ouabain to the right indicating a competitive and reversible displacement. Extracts also produced a dose-dependent inhibition of Na, K ATPase and K-stimulated, p-nitrophenyl phosphatase activity. These results indicate that this ligand may function as an endogenous ligand to the E2 conformation of the Na, K ATPase molecule and be involved in its regulation.
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