PURSUING THE VOLTAGE SENSOR OF A VOLTAGE-GATED MAMMALIAN POTASSIUM CHANNEL

Ion channels are generally classified as voltage- or ligand-gated chan nels based upon their ability to respond to a change in the transmembr ane voltage or to a specific ligand interaction. The voltage sensor of voltage-gated ion channels is thought to be contained within the four th putative transmembrane segment, S4, and is characterized by basic r esidues typically spaced apart. Thus far, a full understanding of all charges contributing to the voltage sensor of voltage-gated potassium channels has been lacking since several neutralization mutants in S4 c ould not be functionally expressed. By construction of multimeric cDNA s encoding a mammalian RCK1 (Kv1.1) potassium channel, we now report f unctional expression of all charge neutralizations in the S4 segment, providing a more comprehensive insight into the functioning of the vol tage sensor.