Tritiated Digoxin Binding to (Na+ + K+)-Activated Adenosine Triphosphatase: Possible Allosteric Site

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Science  19 Apr 1968:
Vol. 160, Issue 3825, pp. 323-325
DOI: 10.1126/science.160.3825.323


Tritiated H3-digoxin specifically binds to a cardiac (Na+ + K+)-activated adenosine triphosphatase. In the presence of adenosine triphosphate and other nucleoside di- and triphosphates, binding is stimulated by sodium ion, the apparent rate constant being similar to that reported for phosphorus-32 incorporation from adenosine triphosphate and for the adenosine triphosphatase activity. In the presence of magnesium, manganese, inorganic phosphate, or other ions, sodium ion inhibits binding. The data support an allosteric type of sodium-potassium ion pump.

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