Comparison of inactivation in NvShak channels.

<p><b><i>(a)</i></b> Comparison of inactivation time course in NvShak1, NvShak4 and NvShak5 currents recorded from excised patches in response to a depolarization to +60 mV. Currents were recorded in 2 mM external K⁺ and were normalized by peak amplitude to facilitate comparison of inactivation. Scale bar indicates time. <b><i>(b)</i></b> Steady state inactivation curves are given for NvShak1, NvShak4, NvShak5 and NvShak6. Data points show mean peak current ± S.E.M. (n = 4–6) elicited during a +60 mV test pulse following a 5 s pre-pulse to the indicated voltage. Data from individual patches were normalized in amplitude prior to comparison. Curves represent single Boltzmann distribution fits; V₅₀ and slope values are reported in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051366#pone-0051366-t001" target="_blank">Table 1</a>. Currents elicited at +60 mV for wild type (WT, black) and N-terminal truncated (Trunc, red) versions of NvShak1, NvShak5 and NvShak4 are compared in <b><i>c-e</i></b>, respectively. Currents were normalized in amplitude for display. Truncations eliminated amino acid residues 2–30, 2–48 and 2–58 for NvShak1, NvShak4 and NvShak5, respectively. Truncation eliminated fast inactivation in NvShak1 and NvShak5, but only reduced the rate of inactivation in NvShak4. 140 mM K+ had little effect on the inactivation time course of WT NvShak4 (gray) but eliminated residual inactivation in the truncated form of NvShak4 (dark red), suggesting an unmasked C-type inactivation process in the truncated channel.