The S. cerevisiae outwardly-rectifying potassium channel (DUK1) identifies a new family of channels with duplicated pore domains.

Potassium channel subunits have six or two transmembrane segments in addition to a conserved pore-forming (P) domain; four subunits come together to form a channel. A gene was identified in S. cerevisiae (J0911) encoding a protein with eight probable membrane-spanning segments and two such P regions. This protein (Duk1p) is a potassium channel because Xenopus oocytes injected with the corresponding RNA express potassium currents activated by depolarization that are not seen in control oocytes. Similar potassium currents were recorded from wildtype S. cerevisiae spheroplasts, but not from those in which the DUK1 locus had been disrupted. Cells carrying the duk1 delta 1::HIS disruption in addition to a chimeric gene comprising DUK1 behind the GAL1 promoter showed outward currents when grown in galactose, but not when grown in glucose. Additional sequences with the duplicate pore motif were found in C. elegans, suggesting that these proteins represent a novel structural family of potassium channel proteins.