Modulation of pump function by mutations in the first transmembrane region of Na+-K+-ATPase alpha1-subunit

The role of amino acid cysteine (Cys) on ion transport activity in the first transmembrane region of the Na+-K+-adenosinetriphosphatase (ATPase) alpha1-subunit was investigated by measuring the current generated by the Na+-K+ pump in HeLa cells using the patch-clamp method. Na+-K+-ATPase in endogenous cells was inhibited when cells were grown in ouabain, suggesting differences in the sensitivity of the cells to ouabain. Cells exposed to ouabain displayed external K+-dependent pump currents, suggesting that mutations reduced K+ affinity to the pump.