On the kaliotoxin and dendrotoxin binding sites on rat brain synaptosomes

The toxic polypeptides alpha- beta-, gamma- and delta-dendrotoxin (DTX), kn own to be potent blockers of voltage-dependent potassium channels of the K nu 1 family, were purified from the venom of the green mamba Dendroaspis an gusticeps. Their binding behaviour to synaptosomal membranes of rat brain w as analysed and compared with that of kaliotoxin (KTX), in a competition as say using [I-125] KTX. alpha-DTX and delta-DTX were found to compete with r adioiodinated-KTX (IC50 of 8 pM and 0.2 nM respectively), whereas gamma-DTX did not. Several minor components that competed with radioiodinated-KTX bi nding were identified and characterised chemically and biologically. (C) 20 00 Elsevier Science Ltd. All rights reserved.