kurtoxin kurtoxin kurtoxin is a toxin found in the venom of the scorpion parabuthus transvaalicus. it affects the gating of voltage-gated sodium channels and calcium channels. sources kurtotoxin is found in the venom of the south african scorpion parabuthus transvaalicus. chemistry kurtoxin is a protein containing 63 amino acid residues with a mass of 7386.1 daltons. its formula is c324h478n94o90s8. it can be isolated from the venom of parabuthus transvaalicus by high-performance liquid chromatography (hplc). kurtoxin is closely related to α-scorpion toxins, a family of toxins that slow inactivation of voltage-gated sodium channels. the complete primary amino-acid sequence of kurtoxin is: kidgypvdyw nckricwynn kycndlckgl kadsgycwgw tlscycqglp dnarikrsgr cra. target in research on xenopus oocytes it was found that kurtoxin affects low-threshold α1g and α1h calcium channels, but not the high-threshold α1a, α1b, α1c, and α1e ca channels. like other α-scorpion toxins kurtoxin was also found to interact with voltage-gated sodium channels. in rat neurons, less selectivity for kurtoxin on calcium channels is found. here the toxin interacts with high affinity with t-type, l-type, n-type, and p-type channels. mode of action kurtoxin inhibits ion calcium channels by modifying channel gating. the effect of the toxin is voltage-dependent. in a voltage-clamp experiment it was found that calcium channels are more strongly inhibited by minor depolarization than by a strong depolarization of the cell. the peptide toxin binds close to the channel voltage sensor and thereby produces complex gating modifications specific for each channel type. in rats, kurtoxin inhibited t-type, l-type, and n-type ca channels and facilitated p-type channels. deactivation was accelerated in t-type and l-type channels, slowed down in p-type channels and not affected in n-type calcium channels. kurtoxin also has an effect on sodium channels. it slows down both activation and inactivation of the channel.