Feasibility of non-sense suppression to express Na ⁺ /K ⁺ pumps. (A) Mean current induced by 10 mM K⁺ 3 or 4 d after injection with either WT cRNA or Y780tag mutant cRNA + Tyr-tRNA (NSS-Tyr). The same batches of oocytes were tested on days 3 and 4 after injection. The pump current in oocytes expressing NSS-Tyr was smaller than WT, whether 3 or 4 d after injection. (B) Mean current induced by 10 mM K⁺ in the absence of Na⁺ (left) and apparent dissociation constant K_0.5.K (right) from Hill fits in dose–response curves for K⁺ activation at −50 mV in NMDG⁺ 4 d after injection. Grey circles show individual data points in different oocytes. (C) Mean Q_OFF–V curves measured (125 mM Na⁺, 0 K⁺) for uninjected oocytes and for oocytes injected with WT cRNA, Y780F cRNA, Y780tag cRNA + Tyr-tRNA (NSS-Tyr), or Y780tag cRNA + Phe-tRNA (NSS-Phe). The line plots are the fits to Boltzmann distributions. The inset shows the mean normalized curves illustrating identical voltage dependencies for both pairs: WT NSS-Tyr and Y780F NSS-Phe.