S.J. Gunning et al. Janus-faced atracotoxins block KCa channels The Janus-faced atracotoxins are specific blockers of invertebrate KCa channels Simon J. Gunning1, Francesco J. Maggio2,4, Monique J. Windley1, Stella M. Valenzuela1, Glenn F. King3 and Graham M. Nicholson1 1 Neurotoxin Research Group, Department of Medical & Molecular Biosciences, University of Technology, Sydney, Broadway, NSW 2007, Australia 2 Department of Molecular, Microbial & Structural Biology, University of Connecticut School of Medicine, Farmington, Connecticut 06032, USA and 3 Division of Chemical and Structural Biology, Institute for Molecular Bioscience, University of Queensland, Brisbane QLD 4072, Australia 4 Current affiliation: Bristol-Myers Squibb, 6000 Thompson Road, Syracuse NY 13057, USA Subdivision: Molecular Neurobiology Abbreviations: ACTX, atracotoxin; 4-AP, 4-aminopyridine; BKCa channel, 2+ + 2+ large-conductance Ca -activated K channel; CaV channel, voltage-activated Ca channel; ChTx, charybdotoxin; DRG, dorsal root ganglia; DUM, dorsal unpaired median; EGTA, ethylene glycol-bis(b-aminoethyl ether)-N,N,N’N’-tetraacetic acid; IbTx, + iberiotoxin; J-ACTX, Janus-faced atracotoxin; KA channel, transient ‘A-type’ K channel; 2+ + + KCa channel, Ca -activated K channel; KDR channel, delayed-rectifier K channel; KV + + channel, voltage-activated K channel; NaV channel, voltage-activated Na channel; Slo, Slowpoke; TEA, tetraethylammonium; TTX, tetrodotoxin. RUNNING TITLE: Janus-faced atracotoxins block KCa channels ADDRESS CORRESPONDENCE TO: Graham M. Nicholson, Department of Medical & Molecular Biosciences, University of Technology, Sydney, PO Box 123, Broadway NSW 2007, Australia. Tel: +61 2 9514-2230 Fax: +61 2 9514-2228; E-mail:
[email protected] 1 S.J. Gunning et al. Janus-faced atracotoxins block KCa channels ABSTRACT The Janus-faced atracotoxins are a unique family of excitatory peptide toxins that contain a rare vicinal disulfide bridge.