title: Adenylate cyclase toxin from Bordetella pertussis produces ion conductance across artificial lipid bilayers in a calcium- and polarity-dependent manner.
abstract: Adenylate cyclase toxin (AC toxin) from Bordetella pertussis enters target cells to produce supraphysiologic levels of cAMP and, by a cAMP-independent process, is hemolytic. In the present study, we show for the first time that this toxin also produces ion-permeable, cation-selective pores in phospholipid bilayers. The resulting membrane conductance is absolutely calcium-dependent, as are the intoxication and hemolytic activities. It is strongly affected by the polarity and magnitude of the membrane potential and enhanced by the presence of negatively charged phospholipid. AC toxins from two mutants, BPDE386 and BPD377, which are defective in toxin activity, produce little or no conductance. Finally, evaluation of the current-voltage relationships and the concentration dependence of pore formation and of hemolysis reveal a greater than 3rd power dependence, suggesting that a multimer of AC toxin, probably consisting of three or more holotoxin molecules, is involved in pore formation.
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville 22908.
authors.forename: G
authors.initials: G
authors.lastname: Szabo
authors.forename: M C
authors.initials: MC
authors.lastname: Gray
authors.forename: E L
authors.initials: EL
authors.lastname: Hewlett
mesh_terms: D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity*; D001886:Bordetella pertussis / Q000235:genetics / Q000378:metabolism*; D002118:Calcium; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects; D005798:Genes, Bacterial; D006461:Hemolysis; D007700:Kinetics; D008051:Lipid Bilayers; D008564:Membrane Potentials; D016254:Mutagenesis, Insertional; D011498:Protein Precursors / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity*; D012756:Sheep
chemical_list: D037361:Adenylate Cyclase Toxin; D001426:Bacterial Proteins; D008051:Lipid Bilayers; D011498:Protein Precursors; D000262:Adenylyl Cyclases; D002118:Calcium