The interaction of potassium ions and ATP on the sodium pump of resealed red cell ghosts.

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Abstract
1. Ouabain‐sensitive K or Rb influx was measure into ghosts resealed to contain ATP concentrations of 1 micrometers‐3 mM and no K. 2. Increasing ATP from 1 to 100 micro M, at saturation external K, increased K influx about twentyfold while have no effect on the ratio of ouabain‐sensitive K influx to ouabain‐sensitive ATPase activity. 3. Increasing external K decreased the apparent affinity for ATP. Similarly increasing ATP decreased the apparent affinity for external K. 4. The K influx can be empirically described as: influx = VmaxK2/(K + Kapp)2. Increasing ATP increased Vmax and (Kapp)2 by the same amount. 5. These results are consistent with a consecutive model for the Na pump in which an ATP‐dependent reaction follows a K‐activated dephosphorylation.