Please click here to obtain permission to reproduce this image.
Click on image to view larger version.
Figure 2 Baseline Characteristics of WT and R14C I
Ks Channels
(A) Typical examples of currents recorded from wild-type (WT) (KCNQ1 + KCNE1) and R14C (KCNQ1-R14C + KCNE1) I
Ks channels in Chinese hamster ovary (CHO) cells during 4-s depolarization steps from a holding potential of –80 mV to test potentials in the range –50 to +70 mV followed by repolarization to –60 mV (voltage protocol shown in inset). Scale bars are 0.5 s and 50 pA/pF. Horizontal dashed line indicates zero current level. Solid and dashed arrows indicate points where currents were measured for current-voltage relationships (upper panel to right) and tail currents for isochronal activation curves (lower panel on right), respectively. Tail current data were normalized to the maximum current value (Imax) and fitted with a Boltzmann function: I/Imax = [1 + exp((V0.5 – Vt)/k)]–1, where V0.5 is the half-activation voltage, Vt is the test potential, and k is the slope factor (values for V0.5 and k are summarized in []). (B) Typical examples of currents recorded during 4-s depolarization steps to voltages in the range 0 to +60 mV (voltage protocol shown in inset). Scale bars as for panel A. I
Ks channels undergo transitions through multiple pre-open closed states before finally opening, as indicated by the sigmoidal shape of activation time courses. Rates of activation were estimated by fitting an exponential function (dashed lines) to the second half of the activation time course. Lower panel summarizes the time constants for activation at voltages in the range +20 to +60 mV for WT (red) and R14C (blue)
I
Ks channels. (C) Typical examples of tail currents recorded at voltages in the range –60 mV to –120 mV (voltage protocol shown in inset). Rates of deactivation were obtained by fitting a single exponential to tail current recordings. Lower panel summarizes time constants for deactivation in the range –120 mV to –60 mV for WT (red) and R14C (blue)
I
Ks channels.
|
