Charybdotoxin as an orientation tool for MthK channels. (A) Single-channel MthK traces with 0, 0.72, 7.2, and 72 nM CTX at −200 mV. (B) MthK open probability from a representative bilayer as a function of CTX concentration. Data was fit (smooth line) with the equation
with a K
d of ∼1 nM.