Figure 4: Transfer of the voltage sensor paddle motifs from BgNav1 to Kv2.1.
(a) Sequence alignment of the paddle region of Kv2.1 with the separate S3b–S4 regions of BgNav1 arranged per domain. In BgNav1, the paddle motifs are not identical and are therefore coloured differently: purple, domain I paddle (DI); red, domain II paddle (DII); blue, domain III paddle (DIII); green, domain IV paddle (DIV). In Kv2.1, the paddle motifs are identical and therefore have the same colour (black). Functional chimeras are indicated with a green dot in front of the sequence whereas non-functional chimeras are indicated with a red dot. (b,c) Transfer of the BgNav1 paddle motifs into Kv2.1. Families of potassium currents (b) and tail current voltage–activation relationships (c) for each chimeric construct (n=6; error bars represent s.e.m.). Holding voltage was −90 mV for DI, II, and IV, and −120 mV for DIII, and the tail voltage was −60 mV (−100 mV for DIII). Bars in b are 1 μA and 100 ms. (d) Kinetics of opening and closing for Kv2.1 channels containing paddle motifs from the four domains of BgNav1. Mean time constants (τ) from single-exponential fits to channel activation (filled circles) and deactivation (open circles) are plotted as a function of the voltage at which the current was recorded. n=6, and error bars represent s.e.m. (e) Potassium currents elicited by depolarizations near the foot (less than 1/3 of maximal activation) of the voltage–activation curve (c) for BgNav1/Kv2.1 chimeric constructs. Currents are shown before (black) and following (coloured) addition of 1 μM rDc1a. rDc1a clearly affects only the DII chimera.
