A new family of outwardly rectifying potassium channel proteins with two pore domains in tandem

Nature. 1995 Aug 24;376(6542):690-5. doi: 10.1038/376690a0.


Potassium channels catalyse the permeation of K+ ions across cellular membranes and are identified by a common structural motif, a highly conserved signature sequence of eight amino acids in the P domain of each channel's pore-forming alpha-subunit. Here we describe a novel K+ channel (TOK1) from Saccharomyces cerevisiae that contains two P domains within one continuous polypeptide. Xenopus laevis oocytes expressing the channel exhibit a unique, outwardly rectifying, K(+)-selective current. The channel is permeable to outward flow of ions at membrane potentials above the K+ equilibrium potential; its conduction-voltage relationship is thus sensitive to extracellular K+ ion concentration. In excised membrane patches, external divalent cations block the channel in a voltage-dependent manner, and their removal in this configuration allows inward channel current. These attributes are similar to those described for inwardly rectifying K+ channels, but in the opposite direction, a previously unrecognized channel behaviour. Our results identify a new class of K+ channel which is distinctive in both its primary structure and functional properties. Structural homologues of the channel are present in the genome of Caenorhabditis elegans.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Caenorhabditis elegans
  • Cells, Cultured
  • DNA Primers
  • Drosophila
  • Molecular Sequence Data
  • Oocytes
  • Patch-Clamp Techniques
  • Potassium / metabolism
  • Potassium Channels / chemistry
  • Potassium Channels / genetics
  • Potassium Channels / metabolism*
  • Protein Conformation
  • Recombinant Proteins
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins*
  • Sequence Homology, Amino Acid
  • Sodium / metabolism
  • Xenopus laevis


  • DNA Primers
  • Potassium Channels
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • TOK1 protein, S cerevisiae
  • Sodium
  • Potassium

Associated data

  • GENBANK/U28005