Prevention of opening abolishes the dequenching of fluorescence

(A and B) Ionic (A) and fluorescence (B) signals recorded from TMRM attached at A397C in control conditions and in the presence of 10 mM 4-AP during 100-ms voltage clamp pulses from −80 to +60 mV. 10 mM 4-AP prevented channel opening and reduced current amplitude by 66 ± 6% ( = 3). (C) Mean G-V and F-V relations in the presence of 10 mM 4-AP. and values for G-V and F-V relations were 44.0 ± 2.8 and 23.6 ± 1.7 mV (G-V), and 3.2 ± 2.5 and 18.8 ± 2.1 mV (F-V; = 3). The F-V relation was 41 mV left shifted from the G-V relation. (D and E) Representative ionic (D) and fluorescence (E) signals recorded from A397C in the presence of the ILT mutation during 100-ms voltage clamp pulses to +60 mV. The ILT mutation uncouples independent voltage sensor movement from the concerted opening transition (,) resulting in a shift of the G-V relation to depolarized potentials (see F). (F) Mean G-V and F-V relations for Kv1.5 A397C ILT channels. and values for G-V and F-V relations were 131.0 ± 1.2 and 21.4 ± 0.8 mV (G-V), respectively, and −41.6 ± 1.8 and 20.6 ± 1.7 mV (F-V; = 3). The F-V relation was therefore 173 mV left shifted from the G-V relation.Copyright information:Taken from "Voltage Clamp Fluorimetry Reveals a Novel Outer Pore Instability in a Mammalian Voltage-gated Potassium Channel"The Journal of General Physiology 2008;132(2):209-222.Published online Jan 2008PMCID:PMC2483330.