Figure 3. Biophysical characteristics of KCNQ1 current.

Properties of I _KCNQ1 were developed using experimental data from human KCNQ1 clones expressed in Xenopus laevis oocytes (black) and Chinese hamster cell (gray) [23]–[35], as well as KCNQ-like currents in mouse smooth muscle cells [10]. A, V-dependent activation steady state (n _Q1∞). B, V-dependent steady states for fast inactivation (w _Q1∞) and slow inactivation (s _Q1∞). C, V-dependent activation time constants (τ_{n Q1f} and τ_{n Q1s}). D, fast (τ_{w Q1}) and slow (τ_{s Q1}) inactivation time constants. τ_{w Q1} is V-dependent and fitted to experimental data [23], [26], [27], [30], [33], [35]. τ_{s Q1} is set as a constant at 50 s. This value is chosen to best reproduce the published time tracings from Jensen et al. (2007) [32]. E and F, simulated time tracings of I _KCNQ1 with two different voltage-clamp protocols from [32] (insets) and the experimental time tracings are shown for comparison. (Experimental tracing adapted with permission from Jensen et al. (2007); copyright 2007, Biophysical Society.) G, simulated I-V relationship of I _KCNQ1 using the same voltage-clamp protocol as in E. All I-V data are normalized to the maximal current value at V = 40 mV.