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. 2011 Nov;138(5):521–535. doi: 10.1085/jgp.201110677

Figure 6.

Figure 6.

The S1 segment, not the pore region of hKCNQ1, is important for the modulation by KCNE3. (A) Representative current traces of chimera ciQ1hQ1(S4–S6) in the absence and presence of KCNE3. The membrane potential was stepped up from −100 to +60 mV in 20-mV increments and subsequently stepped to −30 mV for tail currents. Insets are the expanded tail current traces after depolarization to +20, +40, and +60 mV. Expanded areas are indicated by red circles below. Bars in the insets indicate 0.1 s and 0.1 µA, respectively. The “hook” tail current, which reflects de-inactivation and is the characteristic feature of the homomeric KCNQ1 channel, was only seen in the homomeric ciQ1hQ1(S4–S6) channel, indicating that KCNE3 abolished inactivation. (B) G-V relationships for the ciQ1hQ1(S4–S6) in the absence (closed circles) and presence (blue triangles) of KCNE3. The G-V relationships of ciQ1hQ1(S4–S6) in the presence of KCNE1 (red dotted curve) is superimposed for comparison. (C) The constitutive activity indices (G−80mV/G+20mV) with KCNE3 for human KCNQ1 (hKCNQ1; left end), Ci-KCNQ1 (right end), and their chimeras are plotted. Asterisks indicate the significant reduction in the level of G−80mV/G+20mV, with KCNE3 compared with that of hKCNQ1 with KCNE3 (Dunnett’s test). The design for each chimera is depicted at the bottom of the bar graphs; red regions are from human KCNQ1, and blue regions are from Ci-KCNQ1.