This invention relates generally to a new family of potassium channels. More particularly, the present invention relates to the cloning and characterization of a family of distinct trans-membrane potassium ion channels, characterization of such channels, newly identified polynucleotide sequences, polypeptides encoded by such sequences, expression vectors capable of heterologous expression of such polynucleotide sequences, transformed host cells containing the expression vectors, and assay methods and kits therefor for determining the expression of heterologous nucleotide sequences encoding all or a portion of said potassium channels in host cells, chromosome mapping, diagnostic methodologies and kits therefore. Genes encoding potassium channels representative of this family were cloned from Drosophila melanogaster, Caenorhabditis elegans, human and mouse ESTs, and human brain, heart and kidney cDNA libraries. More particularly, the invention arises in part from the determination that the DNA sequences of these genes encode a structurally distinct potassium channel whose molecular architecture is characterized by four membrane spanning domains and two putative pore forming domains.