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. 2019 Jul 4;8:e46170. doi: 10.7554/eLife.46170

Figure 1. Structure and blockade mechanism of the complex CTX/Kv1.2–2.1 paddle chimera.

Figure 1.

(A) Superposition of the blocked and unblocked pore domain Kv-channel structures (PDB:4JTA and 2R9R, respectively). CTX is represented as a transparent surface with the Lys27 ε-amino group occupying the most external ion binding site (S1). Meanwhile both channel backbones are in stick representations (brown for 4JTA and green for 4R9R). Front and back subunits were omitted for clarity. The large superposition of both backbones indicates that the conformational effects of toxin binding are minimal. (B–C) Toxin and channel surfaces are complementary and tight. Surface representation of three pore domains of the blocked Kv-channel (back, left and right) without CTX (B) and with CTX (yellow surface). Note that the external ion binding site is not empty in the toxin bound structure. (D) Cartoon representation of CTX plugging the pore at the external end of the Kv-channel (inspired from MacKinnon and Miller, 1988). The selectivity filter is in equilibrium with internal K+ ions, and its occupation repels the bound toxin. (E) Schematic cartoon of the drop of the electric field along the pore of conductive channels and its alteration in the toxin blocked channel (F), such that some permeant ions movements do not cross the electric field. Lines represent iso-potential curves.