The identification and characterization of a noncontinuous calmodulin-binding site in noninactivating voltage-dependent KCNQ potassium channels

J Biol Chem. 2002 Aug 9;277(32):28545-53. doi: 10.1074/jbc.M204130200. Epub 2002 May 24.


We show here that in a yeast two-hybrid assay calmodulin (CaM) interacts with the intracellular C-terminal region of several members of the KCNQ family of potassium channels. CaM co-immunoprecipitates with KCNQ2, KCNQ3, or KCNQ5 subunits better in the absence than in the presence of Ca2+. Moreover, in two-hybrid assays where it is possible to detect interactions with apo-CaM but not with Ca2+-bound calmodulin, we localized the CaM-binding site to a region that is predicted to contain two alpha-helices (A and B). These two helices encompass approximately 85 amino acids, and in KCNQ2 they are separated by a dispensable stretch of approximately 130 amino acids. Within this CaM-binding domain, we found an IQ-like CaM-binding motif in helix A and two overlapping consensus 1-5-10 CaM-binding motifs in helix B. Point mutations in helix A or B were capable of abolishing CaM binding in the two-hybrid assay. Moreover, glutathione S-transferase fusion proteins containing helices A and B were capable of binding to CaM, indicating that the interaction with KCNQ channels is direct. Full-length CaM (both N and C lobes) and a functional EF-1 hand were required for these interactions to occur. These observations suggest that apo-CaM is bound to neuronal KCNQ channels at low resting Ca2+ levels and that this interaction is disturbed when the [Ca2+] is raised. Thus, we propose that CaM acts as a mediator in the Ca2+-dependent modulation of KCNQ channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Blotting, Western
  • Calmodulin / chemistry*
  • Glutathione Transferase / metabolism
  • Humans
  • KCNQ Potassium Channels
  • KCNQ2 Potassium Channel
  • KCNQ3 Potassium Channel
  • Male
  • Microscopy, Fluorescence
  • Models, Biological
  • Molecular Sequence Data
  • Potassium Channels / chemistry*
  • Potassium Channels / metabolism*
  • Potassium Channels, Voltage-Gated
  • Precipitin Tests
  • Protein Binding
  • Protein Structure, Tertiary
  • Rats
  • Recombinant Fusion Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Transfection
  • Two-Hybrid System Techniques


  • Calmodulin
  • KCNQ Potassium Channels
  • KCNQ2 Potassium Channel
  • KCNQ2 protein, human
  • KCNQ3 Potassium Channel
  • KCNQ3 protein, human
  • KCNQ5 protein, human
  • Kcnq2 protein, rat
  • Kcnq3 protein, rat
  • Kcnq5 protein, rat
  • Potassium Channels
  • Potassium Channels, Voltage-Gated
  • Recombinant Fusion Proteins
  • Glutathione Transferase