title: Tarantula toxins interact with voltage sensors within lipid membranes.
abstract: Voltage-activated ion channels are essential for electrical signaling, yet the mechanism of voltage sensing remains under intense investigation. The voltage-sensor paddle is a crucial structural motif in voltage-activated potassium (K(v)) channels that has been proposed to move at the protein-lipid interface in response to changes in membrane voltage. Here we explore whether tarantula toxins like hanatoxin and SGTx1 inhibit K(v) channels by interacting with paddle motifs within the membrane. We find that these toxins can partition into membranes under physiologically relevant conditions, but that the toxin-membrane interaction is not sufficient to inhibit K(v) channels. From mutagenesis studies we identify regions of the toxin involved in binding to the paddle motif, and those important for interacting with membranes. Modification of membranes with sphingomyelinase D dramatically alters the stability of the toxin-channel complex, suggesting that tarantula toxins interact with paddle motifs within the membrane and that they are sensitive detectors of lipid-channel interactions.
authors.affiliation: Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA. milescum@ninds.nih.gov
authors.forename: Mirela
authors.initials: M
authors.lastname: Milescu
authors.forename: Jan
authors.initials: J
authors.lastname: Vobecky
authors.forename: Soung H
authors.initials: SH
authors.lastname: Roh
authors.forename: Sung H
authors.initials: SH
authors.lastname: Kim
authors.forename: Hoi J
authors.initials: HJ
authors.lastname: Jung
authors.forename: Jae Il
authors.initials: JI
authors.lastname: Kim
authors.forename: Kenton J
authors.initials: KJ
authors.lastname: Swartz
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004594:Electrophysiology / Q000379:methods; D008051:Lipid Bilayers / Q000378:metabolism; D008055:Lipids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009865:Oocytes / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry; D011506:Proteins / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D013111:Spider Venoms / Q000737:chemistry*; D013112:Spiders; D014982:Xenopus laevis / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D008055:Lipids; D015221:Potassium Channels; D011506:Proteins; D013111:Spider Venoms; D010727:Phosphoric Diester Hydrolases; C055160:sphingomyelin phosphodiesterase D