title: Actinobacillus actinomycetemcomitans leukotoxin forms large conductance, voltage-gated ion channels when incorporated into planar lipid bilayers.
abstract: Actinobacillus actinomycetemcomitans leukotoxin is a member of the bacterial RTX (repeats in toxin) toxin family, produced by a diverse group of Gram-negative pathogens. Members of this group of toxins, although similar in sequence, differ in target cell specificity with Actinobacillus actinomycetemcomitans leukotoxin demonstrating a unique species- and cell-type specificity. Purified A. actinomycetemcomitans leukotoxin added to pre-formed POPE/POPS lipid bilayers showed no spontaneous incorporation (to concentrations of 250 ng/ml). Reproducible channel activity was seen when the bilayer was reformed from lipid monolayers in the presence of toxin (50 ng/ml) in one of the aqueous chambers. Control experiments with heat-inactivated toxin did not display channel activity under the same experimental conditions. The channel behavior showed a complex pattern of multiple conductance levels of 118, 262 and 406 pS in solutions containing 0.140 M NaCl. The first two states showed voltage-dependent channel gating with approximately equal but opposite apparent gating charges of 1.4 electrons. A model accounting for the multiple conducting states and gating properties is presented.
authors.affiliation: Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Lear
authors.forename: U G
authors.initials: UG
authors.lastname: Furblur
authors.forename: E T
authors.initials: ET
authors.lastname: Lally
authors.forename: J C
authors.initials: JC
authors.lastname: Tanaka
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000472:pathogenicity*; D001427:Bacterial Toxins / Q000378:metabolism*; D005098:Exotoxins / Q000378:metabolism*; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D005098:Exotoxins; D007473:Ion Channels; D008051:Lipid Bilayers; C018579:leukotoxin