FXYD1 and FXYD6 reduce pump current. (A and B) Mean normalized K⁺_o-induced currents from oocytes expressing α1β1 (n = 40) or α1β1FXYD1 (n = 45; A) and for α1β1 (n = 38) or α1β1FXYD6 (n = 29; B). Each group was normalized to the mean outward current from α1β1 oocytes measured the same day or on subsequent days in seven batches of oocytes in each condition. Error bars are SEM. Normalized data points from individual oocytes are shown as open circles. Asterisks indicate significantly different with respect to α1β1 alone by t test, **, P < 0.001.