Preferential closed channel blockade of HERG potassium currents by chemically synthesised BeKm-1 scorpion toxin

James T Milnes; Christopher E Dempsey; John M Ridley; Olivia Crociani; Annarosa Arcangeli; Jules C Hancox; Harry J Witchel

doi:10.1016/s0014-5793(03)00662-8

Preferential closed channel blockade of HERG potassium currents by chemically synthesised BeKm-1 scorpion toxin

FEBS Lett. 2003 Jul 17;547(1-3):20-6. doi: 10.1016/s0014-5793(03)00662-8.

Authors

James T Milnes¹, Christopher E Dempsey, John M Ridley, Olivia Crociani, Annarosa Arcangeli, Jules C Hancox, Harry J Witchel

Affiliation

¹ Department of Physiology and Cardiovascular Research Laboratories, School of Medical Sciences, University of Bristol, University Walk, BS8 1TD, Bristol, UK.

PMID: 12860380
DOI: 10.1016/s0014-5793(03)00662-8

Abstract

The scorpion toxin peptide BeKm-1 was synthesised by fluorenylmethoxycarbonyl solid phase chemistry and folded by air oxidation. The peptide's effects on heterologous human ether-a-go-go-related gene potassium current (I(HERG)) in HEK293 cells were assessed using 'whole-cell' patch clamp. Blockade of I(HERG) by BeKm-1 was concentration-dependent, temperature-dependent, and rapid in onset and reversibility. Blockade also exhibited inverse voltage dependence, inverse dependence on duration of depolarisation, and reverse use- and frequency-dependence. Blockade by BeKm-1 and recombinant ergtoxin, another scorpion toxin known to block HERG, differed in their recovery from HERG current inactivation elicited by strong depolarisation and in their ability to block HERG when the channels were already activated. We conclude that synthetic BeKm-1 toxin blocks HERG preferentially through a closed (resting) state channel blockade mechanism, although some open channel blockade also occurs.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cation Transport Proteins*
Cell Line
DNA-Binding Proteins*
ERG1 Potassium Channel
Ether-A-Go-Go Potassium Channels
Humans
Kinetics
Patch-Clamp Techniques
Potassium Channel Blockers / chemical synthesis
Potassium Channel Blockers / pharmacology*
Potassium Channels / drug effects
Potassium Channels / genetics
Potassium Channels / physiology*
Potassium Channels, Voltage-Gated*
Protein Folding
Recombinant Proteins / antagonists & inhibitors
Scorpion Venoms / chemical synthesis
Scorpion Venoms / chemistry
Scorpion Venoms / pharmacology*
Thermodynamics
Trans-Activators*
Transcriptional Regulator ERG
Transfection

Substances

BeKm-1 toxin
Cation Transport Proteins
DNA-Binding Proteins
ERG protein, human
ERG1 Potassium Channel
Ether-A-Go-Go Potassium Channels
KCNH2 protein, human
KCNH6 protein, human
Potassium Channel Blockers
Potassium Channels
Potassium Channels, Voltage-Gated
Recombinant Proteins
Scorpion Venoms
Trans-Activators
Transcriptional Regulator ERG