Intracellular domains interactions and gated motions of I(KS) potassium channel subunits

EMBO J. 2009 Jul 22;28(14):1994-2005. doi: 10.1038/emboj.2009.157. Epub 2009 Jun 11.

Abstract

Voltage-gated K(+) channels co-assemble with auxiliary beta subunits to form macromolecular complexes. In heart, assembly of Kv7.1 pore-forming subunits with KCNE1 beta subunits generates the repolarizing K(+) current I(KS). However, the detailed nature of their interface remains unknown. Mutations in either Kv7.1 or KCNE1 produce the life-threatening long or short QT syndromes. Here, we studied the interactions and voltage-dependent motions of I(KS) channel intracellular domains, using fluorescence resonance energy transfer combined with voltage-clamp recording and in vitro binding of purified proteins. The results indicate that the KCNE1 distal C-terminus interacts with the coiled-coil helix C of the Kv7.1 tetramerization domain. This association is important for I(KS) channel assembly rules as underscored by Kv7.1 current inhibition produced by a dominant-negative C-terminal domain. On channel opening, the C-termini of Kv7.1 and KCNE1 come close together. Co-expression of Kv7.1 with the KCNE1 long QT mutant D76N abolished the K(+) currents and gated motions. Thus, during channel gating KCNE1 is not static. Instead, the C-termini of both subunits experience molecular motions, which are disrupted by the D76N causing disease mutation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Fluorescence Resonance Energy Transfer
  • Humans
  • Immunoprecipitation
  • KCNQ1 Potassium Channel / chemistry
  • KCNQ1 Potassium Channel / metabolism*
  • Oocytes
  • Potassium Channels, Voltage-Gated / chemistry
  • Potassium Channels, Voltage-Gated / metabolism*
  • Protein Interaction Domains and Motifs
  • Xenopus

Substances

  • KCNE1 protein, human
  • KCNQ1 Potassium Channel
  • Potassium Channels, Voltage-Gated
  • potassium channel protein I(sk)