FIGURE 4.

Microscopic effects of pH-dependent activation of Kir6.2(F168E) channels. A, continuous record at −50 mV of a tetrameric (FEEE) construct (three copies of Kir6.2(F168E) + one copy of WT Kir6.2), with pH jumps between 6.5 and 8.5 as indicated. Downward deflections at pH changes are solution exchange artifacts and were minimized during figure preparation. The FEEE tetramer was used because it exhibited similar pH dependence as F168E channels but took considerably longer to express currents and was very amenable to recording single channel currents. B, expanded view of channel openings in regions i, ii, and iii indicated in A. Significant changes in single channel current magnitude were not observed, but openings were far more frequent at alkaline pH. Similar observations were made in four patches.