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.

Additional recommended knowledge

Essential Laboratory Skills Guide

Safe Weighing Range Ensures Accurate Results

What is the Correct Way to Check Repeatability in Balances?

Source

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. It can be isolated from the venom of Parabuthus transvaalicus by reversed-phase 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.

References

Chuang, R.S., Jaffe, H., Cribbs, L., Perez-Reyes, E., Schwartz, K.J. (1998). Inhibition of T-type voltage-gated calcium channels by a new scorpion toxin. Nature Neuroscience 1(8), 668-674. [1]

Sidach, S.S., Mintz, I.M. (2002). Kurtoxin, a gating modifier of neuronal high- and low threshold Ca channels. The Journal of Neuroscience, 22(6), 2023-2034. [2]