Figure 7.

Electrical properties of the Δ20–34 channel. (A) Inward-rectifying currents recorded from KAT1 wild type and the channel mutant Δ20–34 were elicited in response to voltage steps to −180 mV to −40 mV in 20-mV increments from a holding voltage of −10 mV. Tail currents were obtained at −50 mV (KAT1 wild type) or −80 mV (channel mutant Δ20–34). (B) Normalized G–V curves calculated for KAT1 wild-type (□, n = 3) and the Δ20–34 channel (▪, n = 3). The composition of the bath solution in A and B was as follows: 50 mM KCl, 90 mM NaCl, 2 mM MgCl₂, 0.5 mM CaCl₂, and 10 mM Hepes (pH 7.2). (C) Deactivation of the Δ20–34 channel. The decline of normalized tail currents from wild-type and Δ20–34 channels evoked at −120 mV after an activating pulse to −150 mV (wild type) or −170 mV (Δ20–34) is shown. (D) I–V curves of the Δ20–34 channels were obtained by 1.5-s ramps from 50 to −200 mV and recorded in the inside-out configuration at different times after patch excision. (E) Effects of low internal pH on the mutant currents elicited by a voltage pulse to −200 mV from a holding voltage of 0 mV in the inside-out configuration of the same macropatch presented in D. The current traces were successively recorded at pH 7.2 and 6.2.