Characterization of a competitive and reversible ligand to E2 conformation of Na, K ATPase molecule.
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.
Rauch
A L
AL
Department of Medicine/Nephrology, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27103.
Buckalew
V M
VM
D000818:Animals; D001667:Binding, Competitive; D004285:Dogs; D004910:Erythrocyte Membrane / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D008024:Ligands; D010042:Ouabain / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011955:Receptors, Drug / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D008024:Ligands; D011955:Receptors, Drug; C028996:cardiac glycoside receptors; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase