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. 2008 Nov;132(5):547–562. doi: 10.1085/jgp.200810051

Figure 9.

Figure 9.

Channel-closing kinetics in the presence of TPrA, TBA, and TPA. (A) Representative traces obtained in the absence (black trace) or presence (gray traces) of 2 and 10 mM TPrA at −100 mV. Tail current kinetics is altered by the presence of the blocker. Channel closure is slowed and the tail currents now display a hook, characteristic of a blocker that interferes with the channel's activation gate. The dotted line represents fits to Eq. 4. (B) Tail currents obtained in the absence (black trace) or presence (gray traces) of 250 μM and 2.5 mM TBA at a voltage of −100 mV. The same behavior as for TPrA is observed, with slowing of the tail currents and the appearance of a hook at the beginning of the repolarization. Dotted lines are fits to Eq. 4. (C) Tail currents obtained in the absence (black trace) and presence (gray trace) of 250 and 500 μM TPA at −100 mV. Channel closure kinetics is slower in the presence of TPA than in its absence, just as for TPrA and TBA. (D) The rate k−1 from fits of Eq. 4 to data as in A was plotted against voltage as an index of the channel's closing rate. The straight lines are fits of equation:
graphic file with name M9.gif
The symbols and parameters of the fit are (n = 5): No TPrA, k−1(0) = 179.86 s−1, z−1 = 0.12 eo (solid circles); 900 μM TPrA, k−1(0) = 164.1 s−1, z−1 = 0.093 eo (solid diamonds); 2 mM TPrA, k−1(0) = 130.3 s−1, z−1 = 0.09 eo (solid squares); 10 mM TPrA, k−1(0) = 128.02 s−1, z−1 = 0.045 eo (solid triangles). (E) As with TPrA, k−1 is plotted as an index of the closing rate as a function of voltage in the presence of TBA. The fit parameters and symbols are (n = 4): No TBA, k−1(0) = 148.01 s−1, z−1 = 0.09 eo (solid circles); 250 μM TBA, k−1(0) = 96.4, z−1 = 0.08 eo (solid diamonds); 500 μM TBA, k−1(0) = 51.2, z−1 = 0.16 eo (solid squares); 2.5 mM TBA, k−1(0) = 60.2, z−1 = 0.13 eo (solid triangles). Group data are presented as mean ± SEM.