A Sequence alignment of the human sodium channel 1.7 (hNav1.7) versus the three T-type calcium channels (sites targeted with mutagenesis highlighted in red). B, Tonic block of human Cav3.1 and Cav3.1 mutants induced by 1 μM application of ProTx I. Domain II mutations are denoted in blue, Domain IV mutations are shown in red [n = 5-6 per channel, at 1 μM]. Note that the last three mutations in Domain IV produced a non-functional channel (NF). Error bars reflect standard errors. Currents were elicited by stepping from a holding potential of −110 mV to a test potential of −20 mV.