Single-channel activity of 1wt/3mut reveals subconductance levels in a range of voltage at which the wt Shaker subunit is closed. (A) Single-channel recordings measured in an oocyte expressing 4wt from an HP of −40 to +70 mV. (B) All-points histograms from the selected traces shown in A at +70 mV (left) and −40 mV (right). (C) Single-channel current amplitude versus voltage relationship of single channels and macro patches of 4wt (n = 6–15; n = 7 of single-channel recordings). (D) Single-channel recordings taken from an oocyte expressing 1wt/3mut at +70 and −70 mV. (E) All-points histograms from selected traces as shown in D at +70 mV (middle) and −70 mV (right). (F) Single-channel current amplitude versus voltage relationship of single channels and macro patches of 1wt/3mut (n = 6–9; n = 6 from single-channel recordings). (G) Ensemble average of the single-channel recordings from the patch shown in D for depolarizations from an HP of −70 to +70 mV (black line) and from an HP −100 to −70 mV (red line). (H) Single-channel recordings taken from another patch of an oocyte expressing 1wt/3mut from an HP of −40 to −70 mV. (I) All-points histogram of the recording shown in H. The dotted lines indicate the level of current in the closed or open channel. Patch clamp experiments. The external and the internal solutions both contained 120 mM K⁺.