Fig. 3.

Pharmacological properties of fluorescently labeled peptide toxins. (A–D) Activation plots for WT Nav1.4 and LBT clones preincubated with 1 μM Ts1-W50Pra. Ts1-W50Pra stays bound to Nav1.4, maintaining its activity after washout. Normalized conductance without toxin pretreatment is shown for WT Nav1.4 (A, black), DI-3GLBT-R(−5) (B, blue), DIII-3GLBT-R(−5) (C, orange), and DIV-3GLBT-R(−5) (D, purple). Green circles indicate normalized conductance in toxin-free solution after treatment with 1 μM Ts1-W50Pra. Dotted lines indicate 5% of the maximum conductance, used here to illustrate the change in activation threshold. Error bars indicate SEMs. The assay using DII-3GLBT was not conducted because the preliminary experiments using DII-3GLBT-R(−5) did not show any effect, which indicates that LBT insertion in DII prevents Ts1 binding. (E) WT Nav1.4 ionic current block by KIIIA-Bodipy (orange circles; IC₅₀ = 108.9 ± 50.4 nM, n = 3–6 cells) and GIIIA-Bodipy (blue circles; IC₅₀ = 336.4 ± 75.4 nM, n = 3–5 cells).