Determination of the subunit stoichiometry of an inwardly rectifying potassium channel.
Inwardly rectifying K+ channels are distantly related to their voltage-gated counterparts and possess a structural motif of only two putative transmembrane segments in each subunit. They are formed by the assembly of an unknown number of subunits. We have examined the subunit stoichiometry of a strongly rectifying K+ channel, IRK1, by linking together the coding sequence of three or four subunits and distinguishing channels with different numbers of subunits carrying a double mutation that alters inward rectification and single-channel properties. We find that IRK1 channels, like voltage-gated K+ channels, are tetrameric channels. Interestingly, the high sensitivity to Mg2+ and polyamines, cations that produce inward rectification by blocking the channel pore from the cytoplasmic side is largely retained in a channel containing only one wild-type subunit and three subunits bearing mutations that abolish high affinity Mg2+ and polyamine block.
Yang
J
J
Howard Hughes Medical Institute, Department of Physiology, University of California, San Francisco 94143-0724, USA.
Jan
Y N
YN
Jan
L Y
LY
D000818:Animals; D004594:Electrophysiology; D005260:Female; D008274:Magnesium / Q000494:pharmacology; D008433:Mathematics; D009154:Mutation; D009865:Oocytes; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D013095:Spermidine / Q000494:pharmacology; D014982:Xenopus laevis
D015221:Potassium Channels; D008274:Magnesium; D013095:Spermidine