Modification of the rate of ouabain binding to (Na+ + K+)ATPase by lithium ions.
We report on the interactions of Li+, a congener of K+ with the (Na+ + K+)-ATPase from E Electricus as measured by their effects on the rate of [3H]-ouabain binding to this enzyme. Like K+, Li+ slows ouabain binding under both Type I (Na+ + ATP) and Type II (P1) conditions, but with lower affinity. In contrast to K+, the Li+ inhibition curve is hyperbolic, suggesting interaction at an uncoupled site. Also differing from the complete inhibition by high K+, a residual ouabain-binding rate persists at high Li+. The interactions of Li+ and K+ are synergistic: the apparent K+ affinity increases 3 to 4-fold in presence of Li+. These results are consistent with the conclusion that Li+ interacts with only one of the two K+ sites and may be of interest in interpreting lithium pharmacology.
D000818:Animals; D004557:Electric Organ / Q000187:drug effects; D004593:Electrophorus; D066298:In Vitro Techniques; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology*; D010042:Ouabain / Q000378:metabolism*; D011188:Potassium / Q000502:physiology; D011485:Protein Binding / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D010042:Ouabain; D008094:Lithium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium