The biophysical properties of T-type voltage-gated calcium channels are wel
l suited to pacemaking and to supporting calcium flux near the resting memb
rane potential in both excitable and nonexcitable cells. We have identified
a new scorpion toxin (kurtoxin) that binds to the alpha(1G) T-type calcium
channel with high affinity and inhibits the channel by modifying voltage-d
ependent gating. This toxin distinguishes between alpha(1G) T-type calcium
channels and other types of voltage-gated calcium channels, including alpha
(1A), alpha(1B), alpha(1C) and alpha(1E). Like the other alpha-scorpion tox
ins to which it is related, kurtoxin also interacts with voltage-gated sodi
um channels and slows their inactivation. Kurtoxin will facilitate characte
rization of the subunit composition of T-type calcium channels and help det
ermine their involvement in electrical and biochemical signaling.