Recent studies on dendrotoxins and potassium ion channels

Dendrotoxins are small proteins isolated from mamba (Dendroaspis) snake venoms. They block some subtypes of voltage-dependent potassium channels in neurons. Dendrotoxins contain 57-60 amino acid residues crosslinked by three disulfide bridges. They are homologous to Kunitz-type serine protease inhibitors, such as aprotinin, although they have little or no antiprotease activity. Dendrotoxins act mainly on neuronal K+ channels. Studies with cloned K+ channels indicate that alpha-dendrotoxin from green mamba Dendroaspis angusticeps blocks Kv1.1 and Kv1.2 channels in the nanomolar range. In native cells, dendrotoxin appears preferentially to block inactivating forms of K+ current. Dendrotoxins can induce repetitive firing in neurons and facilitate transmitter release. On direct injection to the CNS, dendrotoxins can induce epileptiform activity. Radiolabeled dendrotoxins are useful markers of subtypes of K+ channels in vivo, and structural analogs help to define the molecular recognition properties of different types of K+ channels.