A new family of outwardly rectifying potassium channel proteins with two pore domains in tandem.
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.
Ketchum
K A
KA
Department of Pediatrics, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536-0812, USA.
Joiner
W J
WJ
Sellers
A J
AJ
Kaczmarek
L K
LK
Goldstein
S A
SA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans; D002478:Cells, Cultured; D017931:DNA Primers; D004330:Drosophila; D008969:Molecular Sequence Data; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D014982:Xenopus laevis
D017931:DNA Primers; D015221:Potassium Channels; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C095220:TOK1 protein, S cerevisiae; D012964:Sodium; D011188:Potassium