Distinct roles of the last transmembrane domain in controlling Arabidopsis K+ channel activity

New Phytol. 2009;182(2):380-91. doi: 10.1111/j.1469-8137.2008.02749.x. Epub 2009 Jan 14.


The family of voltage-gated potassium channels in plants presumably evolved from a common ancestor and includes both inward-rectifying (K(in)) channels that allow plant cells to accumulate K(+) and outward-rectifying (K(out)) channels that mediate K(+) efflux. Despite their close structural similarities, the activity of K(in) channels is largely independent of K(+) and depends only on the transmembrane voltage, whereas that of K(out) channels responds to the membrane voltage and the prevailing extracellular K(+) concentration. Gating of potassium channels is achieved by structural rearrangements within the last transmembrane domain (S6). Here we investigated the functional equivalence of the S6 helices of the K(in) channel KAT1 and the K(out) channel SKOR by domain-swapping and site-directed mutagenesis. Channel mutants and chimeras were analyzed after expression in Xenopus oocytes. We identified two discrete regions that influence gating differently in both channels, demonstrating a lack of functional complementarity between KAT1 and SKOR. Our findings are supported by molecular models of KAT1 and SKOR in the open and closed states. The role of the S6 segment in gating evolved differently during specialization of the two channel subclasses, posing an obstacle for the transfer of the K(+)-sensor from K(out) to K(in) channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arabidopsis / chemistry
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Cell Membrane / metabolism*
  • Computer Simulation
  • Models, Biological
  • Models, Molecular
  • Models, Structural
  • Mutation
  • Oocytes
  • Potassium Channels, Inwardly Rectifying / chemistry*
  • Potassium Channels, Inwardly Rectifying / metabolism
  • Potassium Channels, Voltage-Gated / chemistry*
  • Potassium Channels, Voltage-Gated / metabolism*
  • Sequence Alignment
  • Shaker Superfamily of Potassium Channels / chemistry*
  • Shaker Superfamily of Potassium Channels / genetics
  • Shaker Superfamily of Potassium Channels / metabolism
  • Xenopus


  • Arabidopsis Proteins
  • KAT1 protein, Arabidopsis
  • Potassium Channels, Inwardly Rectifying
  • Potassium Channels, Voltage-Gated
  • SKOR protein, Arabidopsis
  • Shaker Superfamily of Potassium Channels