Inhibition of T-type voltage-gated calcium channels by a new scorpion toxin

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Abstract
The biophysical properties of T-type voltage-gated calcium channels are well suited to pacemaking and to supporting calcium flux near the resting membrane potential in both excitable and non-excitable cells. We have identified a new scorpion toxin (kurtoxin) that binds to the α 1G T-type calcium channel with high affinity and inhibits the channel by modifying voltage-dependent gating. This toxin distinguishes between α 1G T-type calcium channels and other types of voltage-gated calcium channels, including α 1A , α 1B , α 1C and α 1E . Like the other α-scorpion toxins to which it is related, kurtoxin also interacts with voltage-gated sodium channels and slows their inactivation. Kurtoxin will facilitate characterization of the subunit composition of T-type calcium channels and help determine their involvement in electrical and biochemical signaling.