Structure and function of scorpion toxins affecting K+-channels

This chapter reviews current literature dealing with peptides isolated from the venom of scorpions. Only peptides that recognize K+-channels are repor ted. They are called K+-channel-ligands or simply peptides, because the act ual toxicity effects of all these peptides has not been demonstrated. The p rimary structures of 35 peptides are reviewed, and a general nomenclature h as been proposed to define 9 distinct sub-families of related sequences. Pa rtial sequences were not included in this classification. They are 29 to 39 amino acid residues long peptides with a common structural motif composed of an alpha-helix segment and three anti-parallel beta-sheet strands stabil ized by three or four disulfide bridges. Binding and/or electrophysiologica l experiments showed that the affinity of these peptides for the various su b-types of K+-channels varies from micromolar to picomolar concentrations. Some data on the three-dimensional structures and on specific functions of the various peptides on voltage-dependent K+-channels, high-conductance and small-conductance, Ca2+-dependent K+-channels are also briefly reviewed.