Calcicludine is a toxin in the venom of the green mamba (Dendroaspis angusticeps).
Calcicludine is a 60-amino acid polypeptide with six cysteines forming three disulfide bridges.
Calcicludine structurally resembles dendrotoxin, but works differently, since even at high concentrations, calcicludine has no effect on dendrotoxin-sensitive potassium channels in chicken and rat neurons.
For example, the IC50 for block of L-type calcium channels on a cerebellar granule cell is 0.2 nM, but the IC50 of the block of rat peripheral DRG neuronal L-type channels is around 60-80 nM.
It has been suggested to act by a partial pore block or an effect on channel gating.