Functional analysis of an archaebacterial voltage-dependent K+ channel

All living organisms use ion channels to regulate the transport of ions across cellular membranes'. Certain ion channels are classed as voltage-dependent because they have a voltage-sensing structure that induces their pores to open in response to changes in the cell membrane voltage. Until recently, the voltage-dependent K+, Ca2+ and Na+ channels were regarded as a unique development of eukaryotic cells, adapted to accomplish specialized electrical signalling, as exemplified in neurons. Here we present the functional characterization of a voltage-dependent K+ (K-V) channel from a hyperthermophilic archaebacterium from an oceanic thermal vent. This channel possesses all the functional attributes of classical neuronal K-V channels. The conservation of function reflects structural conservation in the voltage sensor as revealed by specific, high-affinity interactions with tarantula venom toxins, which evolved to inhibit eukaryotic K-V channels.