Localization of the ergtoxin-1 receptors on the voltage sensing domain of hERG K+ channel by AFM recognition imaging

Pflugers Arch. 2008 Apr;456(1):247-54. doi: 10.1007/s00424-007-0418-9. Epub 2008 Feb 20.


The inhibition of the human ether-à-go-go-related (hERG) K+ channels is the major cause of long QT syndromes inducing fatal cardiac arrhythmias. Ergtoxin 1 (ErgTx1) belongs to scorpion-toxins, which are K+ channel-blockers, and binds to hERG channel with 1:1 stoichiometry and high affinity (Kd approximately 10 nM). Nevertheless, patch-clamp recordings recently demonstrated that ErgTx1 does not establish complete blockade of hERG currents, even at high ErgTx1 concentrations. Such phenomenon is supposed to be consistent with highly dynamic conformational changes of the outer pore domain of hERG. In this study, simultaneous topography and recognition imaging (TREC) on hERG HEK 293 cells was used to visualize binding sites on the extracellular part of hERG channel (on S1-S2 region) for Anti-Kv11.1 (hERG-extracellular-antibody). The recognition maps of hERG channels contained recognition spots, haphazardly distributed and organized in clusters. Recognition images after the addition of ErgTx1 at high concentrations ( approximately 1 microM) revealed subsequent partial disappearance of clusters, indicating that ErgTx1 was bound to the S1-S2 region. These results were supported by AFM force spectroscopy data, showing for the first time that voltage sensing domain (S1-S4) of hERG K+ channel might be one of the multiple binding sites of ErgTx1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies / immunology
  • Cell Line
  • Ether-A-Go-Go Potassium Channels / immunology
  • Ether-A-Go-Go Potassium Channels / ultrastructure*
  • Humans
  • Kidney / cytology
  • Kidney / embryology
  • Kidney / ultrastructure
  • Microscopy, Atomic Force / methods*
  • Protein Binding
  • Protein Structure, Tertiary
  • Receptors, Cell Surface / metabolism*
  • Receptors, Cell Surface / ultrastructure*
  • Scorpion Venoms / metabolism*


  • Antibodies
  • Ether-A-Go-Go Potassium Channels
  • Receptors, Cell Surface
  • Scorpion Venoms
  • ergotoxin, Centruroides noxius