- Kurtoxin
Kurtoxin is a toxin found in the venom of the scorpion "
Parabuthus transvaalicus ". It affects the gating of voltage-gatedsodium channels andcalcium channels .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 7386.1daltons . It can be isolated from the venom of "Parabuthus transvaalicus" by reversed-phasehigh-performance liquid chromatography (HPLC). Kurtoxin is closely related to α-scorpion toxins, a family of toxins that slow inactivation ofvoltage-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-gatedsodium channels . In rat neurons, less selectivity for kurtoxin oncalcium 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 minordepolarization 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 onsodium 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. [http://www.jneurosci.org/cgi/reprint/22/6/2023]
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. [http://jpet.aspetjournals.org/cgi/reprint/314/3/1370]
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