K+ selective channels are some of the most widespread ion trafficking molecules in living organisms, with more than 70 genes encoding different K+ channels in humans. 38 of those genes encode members of the KV channel super family. KV channels are composed of two types of protein subunits: the (A) subunit, which forms the pore and auxiliary ((B)) subunits. (A) subunits tetramerize in order to form a functional K+ conducting channel. The KV (A) subunit is a protein with six transmembrane (TM) domains and intracellular N- and C-termini. The most defined structural features are the extracellular loop between the fifth and sixth TM (which forms the K+ selectivity filter and the channel pore) and the fourth TM, which is positively charged and forms the voltage sensor of the protein.
The pharmacological profile of KV channels is quite impressive. Due to the large number and types of functional KV channels, it became very important to identify the different native KV currents in different tissues, cell types and developmental stages. Therefore, molecules that can specifically bind KV channel components have become powerful tools in characterizing both the channel structure and its physiological role. Peptidyl toxins, mainly from scorpion and snake venoms, play a major role in identifying the various KV channels. Such toxins include dendrotoxins from the green and black mamba snakes and agitoxins from scorpions.