title: Preferential closed channel blockade of HERG potassium currents by chemically synthesised BeKm-1 scorpion toxin.
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.
authors.affiliation: Department of Physiology and Cardiovascular Research Laboratories, School of Medical Sciences, University of Bristol, University Walk, BS8 1TD, Bristol, UK.
authors.forename: James T
authors.initials: JT
authors.lastname: Milnes
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Dempsey
authors.forename: John M
authors.initials: JM
authors.lastname: Ridley
authors.forename: Olivia
authors.initials: O
authors.lastname: Crociani
authors.forename: Annarosa
authors.initials: A
authors.lastname: Arcangeli
authors.forename: Jules C
authors.initials: JC
authors.lastname: Hancox
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Witchel
mesh_terms: D027682:Cation Transport Proteins; D002460:Cell Line; D004268:DNA-Binding Proteins; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D006801:Humans; D007700:Kinetics; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000138:chemical synthesis / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D017510:Protein Folding; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D012604:Scorpion Venoms / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013816:Thermodynamics; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG; D014162:Transfection
chemical_list: C425305:BeKm-1 toxin; D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; C072312:ERG protein, human; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; D012604:Scorpion Venoms; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG