The Journal of General Physiology
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Published online October 15, 2007
doi:10.1085/jgp.200709869
The Journal of General Physiology, Vol. 130, No. 5, 497-511
The Rockefeller University Press, 0022-1295 $30.00
© 2007 Milescu et al.
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ARTICLE

 Tarantula Toxins Interact with Voltage Sensors within Lipid Membranes



Mirela Milescu1, Jan Vobecky1, Soung H. Roh2, Sung H. Kim2, Hoi J. Jung2, Jae Il Kim2, and Kenton J. Swartz1

1 Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
2 Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, 500-712, Korea

Correspondence to Mirela Milescu: milescum{at}ninds.nih.gov; or Kenton J. Swartz: swartzk{at}ninds.nih.gov

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 (Kv) 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 Kv 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 Kv 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.

Abbreviations used in this paper: CD, circular dichroism; LUV, large unilamellar vesicle; PB, physiological buffer; POPC, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine; POPG, 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)]; SM, sphingomyelin; SMaseD, sphingomyelinase D; WT, wild type.


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