Origins of the different sensitivities of (Na+ + K+)-dependent adenosinetriphosphatase preparations to ouabain.
Properties of the Na+, K+-ATPase preparations from rat and dog kidney medullae were compared. The two enzymes, with a 1000-fold difference in ouabain sensitivities, had similar subunit compositions and similar K0.5 values and Hill coefficients for substrates and activators of several catalytic activities; suggesting that the structural differences of the two are limited to the ouabain binding domains. Experiments on the interactions of ouabain, Pi, and Mg2+ with the enzymes showed that the two enzymes differed (a) in their inherent affinities for ouabain; and (b) in that Mg2+ binding increased affinity for ouabain to a greater extent in the dog enzyme than in the rat enzyme.
D000818:Animals; D004285:Dogs; D007679:Kidney Medulla / Q000201:enzymology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009840:Oligomycins / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology*; D011485:Protein Binding; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013045:Species Specificity; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology
D009840:Oligomycins; D014639:Vanadium; D014638:Vanadates; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium