Distinct amino acids in the C-linker domain of the Arabidopsis K+ channel KAT2 determine its subcellular localization and activity at the plasma membrane

Plant Physiol. 2014 Mar;164(3):1415-29. doi: 10.1104/pp.113.229757. Epub 2014 Jan 9.


Shaker K(+) channels form the major K(+) conductance of the plasma membrane in plants. They are composed of four subunits arranged around a central ion-conducting pore. The intracellular carboxy-terminal region of each subunit contains several regulatory elements, including a C-linker region and a cyclic nucleotide-binding domain (CNBD). The C-linker is the first domain present downstream of the sixth transmembrane segment and connects the CNBD to the transmembrane core. With the aim of identifying the role of the C-linker in the Shaker channel properties, we performed subdomain swapping between the C-linker of two Arabidopsis (Arabidopsis thaliana) Shaker subunits, K(+) channel in Arabidopsis thaliana2 (KAT2) and Arabidopsis thaliana K(+) rectifying channel1 (AtKC1). These two subunits contribute to K(+) transport in planta by forming heteromeric channels with other Shaker subunits. However, they display contrasting behavior when expressed in tobacco mesophyll protoplasts: KAT2 forms homotetrameric channels active at the plasma membrane, whereas AtKC1 is retained in the endoplasmic reticulum when expressed alone. The resulting chimeric/mutated constructs were analyzed for subcellular localization and functionally characterized. We identified two contiguous amino acids, valine-381 and serine-382, located in the C-linker carboxy-terminal end, which prevent KAT2 surface expression when mutated into the equivalent residues from AtKC1. Moreover, we demonstrated that the nine-amino acid stretch 312TVRAASEFA320 that composes the first C-linker α-helix located just below the pore is a crucial determinant of KAT2 channel activity. A KAT2 C-linker/CNBD three-dimensional model, based on animal HCN (for Hyperpolarization-activated, cyclic nucleotide-gated K(+)) channels as structure templates, has been built and used to discuss the role of the C-linker in plant Shaker inward channel structure and function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Amino Acid Substitution
  • Amino Acids / metabolism*
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry*
  • Arabidopsis Proteins / metabolism*
  • Cell Membrane / metabolism*
  • Ion Channel Gating
  • Models, Molecular
  • Molecular Sequence Data
  • Point Mutation / genetics
  • Potassium Channels, Voltage-Gated / chemistry*
  • Potassium Channels, Voltage-Gated / metabolism*
  • Protein Structure, Tertiary
  • Protein Transport
  • Sequence Deletion / genetics
  • Structural Homology, Protein
  • Structure-Activity Relationship
  • Subcellular Fractions / metabolism


  • Amino Acids
  • Arabidopsis Proteins
  • KAT2 protein, Arabidopsis
  • Potassium Channels, Voltage-Gated