Figure 2.

E208K and V324M enhance channel response to MgADP by affecting transduction of the MgADP effect to Kir6.2. Inside-out patch recordings were performed similar to that shown in Fig. 1, C and D, by exposing channels to 0.1 mm ATP or 0.1 mm ATP+0.5 mm ADP (free [Mg²⁺] ∼1 mm). The currents relative to those observed in K-INT solution immediately after patch excision were quantified. A, The E1507K inactivating mutation in NBF2 completely abolished the activating effects of E208K or V324M. Each bar is the mean ± sem of three or four patches. B, Effects of the activating mutations in TMD0-L0 and TMD1 are additive. Each bar is the mean ± sem of 30 (WT), eight (E208K), six (L225P), five (V324M), nine (E208K/L225P), six (E208K/V324M), and six (L225P/V324M) patches. *, P < 0.05 for comparison between mutant and WT by one-way ANOVA with Dunnett’s post hoc test. #, P < 0.05 for comparison between each double mutant and its respective single mutants. (#), P < 0.05 between E208K/V324M and E208K but the difference between E208K/V324M and V324M is not significant.