Comparison of the magnitude of ouabain-sensitive inward current in each pump type at −180 mV (−160 mV for WT) in the absence or presence of 125 mM Nao after normalization by the ouabain-sensitive pump current activated by 15 mM [Ko] at the −50-mV holding potential in the same oocyte and [Nao] to allow for differences in expression. Open bars, absence of 125 mM Nao; closed bars, presence of 125 mM Nao. Mean values are −0.04 ± 0.02, n = 4, in 125 mM Nao and −0.17 ± 0.05, n = 4, in 0 mM Nao for WT Na/K pumps (black); −0.20 ± 0.03, n = 8, in 125 mM Nao and −2.0 ± 0.1, n = 8, in 0 mM Nao for C113Y (red); −2.6 ± 0.4, n = 5, in 125 mM Nao and −2.8 ± 0.4, n = 5, in 0 mM Nao for C113Y-ΔKESYY (blue); −1.8 ± 0.2, n = 6, in 125 mM Nao and −3.2 ± 0.6, n = 6, in 0 mM Nao for C113Y-ΔYY (olive); −0.10 ± 0.02, n = 7, in 125 mM Nao and −1.9 ± 0.1, n = 7, in 0 mM Nao for RD (green); −1.6 ± 0.1, n = 8, in 125 mM Nao and −0.43 ± 0.03, n = 8, in 0 mM Nao for RD-ΔKESYY (magenta); and −1.9 ± 0.1, n = 7, in 125 mM Nao and −0.60 ± 0.08, n = 7, in 0 mM Nao for RD-ΔYY (orange). Error bars represent SEM.