title: Topology of the amphipathic helices of the colicin A pore-forming domain in E. coli lipid membranes studied by pulse EPR.
abstract: Colicin A is a water-soluble pore-forming protein that kills cells, which are not protected by an immunity protein, by inserting specific helical segments of the toxin subdomain into the cytoplasmic membrane to form voltage-dependent ion channels. This leads to depolarization of the cell membrane followed by depletion of the intracellular ATP levels and finally to cell death. The formation of the integral membrane voltage-gated ion channel is known to be accompanied by a conformational transition. Using double electron electron resonance spectroscopy inter-spin distances in doubly spin labeled colicin A mutants, with spin labels bound to positions 42/187, 62/187, 91/187 and 115/187, have been determined to serve as constraints for the modeling of the membrane bound, closed channel state of colicin A. The data reveal a quasi-circular arrangement of the eight amphipathic helices, embedded in the membrane interfacial layer close to the lipid-water interface, whereas the two hydrophobic helices are buried within the membrane.
authors.affiliation: Department of Physics, University of Osnabrück, Barbarastrasse 7, D-49069 Osnabrück, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Böhme
authors.forename: Pulagam V L
authors.initials: PV
authors.lastname: Padmavathi
authors.forename: Julia
authors.initials: J
authors.lastname: Holterhues
authors.forename: Fatiha
authors.initials: F
authors.lastname: Ouchni
authors.forename: Johann P
authors.initials: JP
authors.lastname: Klare
authors.forename: Heinz-Jürgen
authors.initials: HJ
authors.lastname: Steinhoff
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D003087:Colicins / Q000737:chemistry* / Q000235:genetics; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D008051:Lipid Bilayers / Q000737:chemistry*; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D013113:Spin Labels; D053835:Unilamellar Liposomes / Q000737:chemistry
chemical_list: D003087:Colicins; D008051:Lipid Bilayers; D011994:Recombinant Proteins; D013113:Spin Labels; D053835:Unilamellar Liposomes