title: Release of lipid vesicle contents by the bacterial protein toxin alpha-haemolysin.
abstract: alpha-Haemolysin is a protein toxin (107 kDa) secreted by some pathogenic strains of E. coli. It binds to mammalian cell membranes, disrupting cellular activities and lysing cells. This paper describes the mechanism of alpha-haemolysin-induced membrane leakage, from experiments in which extrusion large unilamellar vesicles, loaded with fluorescent solutes, are treated with purified toxin. The results show that the toxin does not require of any membrane receptor to exert its activity, that vesicles become leaky following an 'all-or-none' mechanism, and that leakage occurs through a non-osmotic detergent-like bilayer disruption induced by the protein. Small pores formed by monomeric alpha-haemolysin, as described by other authors, do not appear to be related to the process of membrane disruption. Instead, the experimental data would be in agreement with the idea of oligomeric assemblies being required to produce release of solutes from a single vesicle.
authors.affiliation: Department of Biochemistry, University of the Basque Country, Bilbao, Spain.
authors.forename: H
authors.initials: H
authors.lastname: Ostolaza
authors.forename: B
authors.initials: B
authors.lastname: Bartolomé
authors.forename: I
authors.initials: I
authors.lastname: Ortiz de Zárate
authors.forename: F
authors.initials: F
authors.lastname: de la Cruz
authors.forename: F M
authors.initials: FM
authors.lastname: Goñi
mesh_terms: D001426:Bacterial Proteins / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000494:pharmacology*; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects; D003902:Detergents / Q000494:pharmacology; D003911:Dextrans / Q000378:metabolism; D029968:Escherichia coli Proteins; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism / Q000031:analogs & derivatives; D006460:Hemolysin Proteins / Q000494:pharmacology*; D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000378:metabolism*; D008563:Membrane Lipids / Q000032:analysis / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003902:Detergents; D003911:Dextrans; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D011956:Receptors, Cell Surface; C015219:fluorescein isothiocyanate dextran; D016650:Fluorescein-5-isothiocyanate