Inhibition of the Ca^2v+-activated K⁺-channel by sapecin B, an insect antibacterial protein

Sapecin is an antibacterial protein of the flesh fly and sapecin B is its homologue structurally similar to charybdotoxin of scorpion venom, which is known to be a K⁺ channel inhibitor. We found that, like charybdotoxin, sapecin B inhibits part of the voltage pulse-induced K⁺ currents of rat cerebellar Purkinje cells. We suggest that this effect is due to inhibition of the Ca⁺-activated K⁺ channel. Probably, sapecin B is a naturally occurring K⁺ channel inhibitor as well as an antibacterial protein.