Modulation of HERG gating by a charge cluster in the N-terminal proximal domain

Biophys J. 2006 Dec 15;91(12):4381-91. doi: 10.1529/biophysj.106.087247. Epub 2006 Sep 22.

Abstract

Human ether-a-go-go-related gene (HERG) potassium channels contribute to the repolarization of the cardiac action potential and display unique gating properties with slow activation and fast inactivation kinetics. Deletions in the N-terminal 'proximal' domain (residues 135-366) have been shown to induce hyperpolarizing shifts in the voltage dependence of activation, suggesting that it modulates activation. However, we did not observe a hyperpolarizing shift with a subtotal deletion designed to preserve the local charge distribution, and other deletions narrowed the region to the KIKER containing sequence 362-372. Replacing the positively charged residues of this sequence by negative ones (EIEEE) resulted in a -45 mV shift of the voltage dependence of activation. The shifts were intermediate for individual charge reversals, whereas E365R resulted in a positive shift. Furthermore, the shifts in the voltage dependence were strongly correlated with the net charge of the KIKER region. The apparent speeding of the activation was attributable to the shifted voltage dependence of activation. Additionally, the introduction of negative charges accelerated the intermediate voltage-independent forward rate constant. We propose that the modulatory effects of the proximal domain on HERG gating are largely electrostatic, localized to the charged KIKER sequence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • ERG1 Potassium Channel
  • Electromagnetic Fields*
  • Ether-A-Go-Go Potassium Channels / genetics
  • Ether-A-Go-Go Potassium Channels / physiology*
  • Humans
  • Ion Channel Gating*
  • Mutation
  • Patch-Clamp Techniques
  • Protein Structure, Tertiary
  • Static Electricity

Substances

  • ERG1 Potassium Channel
  • Ether-A-Go-Go Potassium Channels
  • KCNH2 protein, human