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

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.