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. 2011 May 3;589(Pt 13):3071–3083. doi: 10.1113/jphysiol.2011.209700

Figure 3. Effect of the W68R mutation on ATP sensitivity in the absence and presence of Mg2+.

Figure 3

A, representative currents recorded at −60 mV from inside-out patches expressing wild-type (Kir6.2/SUR1), hetW68R or homW68R channels. Patches were exposed to 100 μm ATP as indicated by the lower bar. The dotted line indicates the zero current level. The x-axis scale bar is 10 s, and the y-axis scale bar is 500 pA (Kir6.2/SUR1), 500 pA (hetW68R) and 100 pA (homW68R). B and C, mean relationship between [ATP] and KATP current (I), expressed relative to the current in the absence of nucleotide (Ic) for Kir6.2/SUR1 (open circles), heterozygous (filled circles) and homomeric (filled triangles) Kir6.2-W68R/SUR1 channels. Experiments were carried out in the absence (B) or presence (C) of 2 mm Mg2+. The smooth curves are the best fit of eqn (1) to the data. Mg-free: WT IC50 = 10 μm, h = 1.15 (n = 9); hetW68R IC50 = 27 μm, h = 0.87 (n = 9); homW68R IC50 = 50 μm, h = 1.0 (n = 7). 2 mm Mg2+: WT IC50 = 15 μm, h = 1.01 (n = 26); hetW68R IC50 = 37 μm, h = 0.85, a = 0.005 (n = 12); homW68R IC50 = 146 μm, h = 0.88, a = 0.014 (n = 13).