Interaction of Sodium and Potassium Ions with Na+,K+ ATpase. III. Cooperative Effect of ATP and Na+ on Complete Release of K+ from E2K

• Published in: Journal of biochemistry (Tokyo) Vol. 101; no. 3; pp. 789 - 793
• Main Authors: HOMAREDA, Haruo, NOZAKI, Tadashi, MATSUI, Hideo
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.03.1987
• Subjects: Adenosine Triphosphate - metabolism; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Dogs; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydrolases; Kidney Medulla - enzymology; Kidney Medulla - ultrastructure; Magnesium - metabolism; Microsomes - enzymology; Ouabain - metabolism; Potassium - metabolism; Sodium - metabolism; Sodium Chloride - pharmacology; Sodium-Potassium-Exchanging ATPase - metabolism; Fissipedia; Sodium Ions; Carnivora; Molecular form; Enzyme; Interaction; Microsome; Potassium Ions; Synergism; Kidney; Vertebrata; Mammalia; Animal; Na,K-ATPase; Magnesium Ions; Nucleotide; ATP; Dog
• ISSN: 0021-924X; 1756-2651
• DOI: 10.1093/jb/101.3.789

The effects of Na+ and ATP on the K+ binding to Na+,K+-ATPase were investigated by the centrifugation method with radioactive K+ in the absence of Mg2+ In the presence of 10 μM 43KCl 0.6 and 10 mM Na+ decreased the amount of bound K+ to one-half and zero, respectively. On the other hand, 10μM and 10 mM ATP decreased the amount of K+ to 60 and 25–40%, respectively. When the combined effect of ATP and Na+ was tested, 10 μM ATP decreased the Na+ concentration giving half-maximal inhibition of the K+ binding to one-third, showing synergistic inhibition by both ligands, though increase in ATP concentration seemed to depress the inhibitory effect of Na+. The synergistic inhibition by ATP and Na+ suggests that the release of K+ from E2K is not completed by the binding of ATP alone but is completed by the binding of Na+ in addition to ATP during the cycle of Na+,K+-dependent ATP-hydrolysis as well as ion-transport.