title: In vivo EPR on spin labeled colicin A reveals an oligomeric assembly of the pore-forming domain in E. coli membranes.
abstract: We report on the application of site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) spectroscopy to study possible oligomerization of the bacterial toxin colicin A (ColA) upon membrane insertion in vitro and in vivo. We applied SDSL-EPR protocols and optimized experimental conditions to perform continuous wave EPR experiments and double electron-electron resonance distance measurements on intact Escherichia coli cells interacting with nitroxide spin-labeled ColA. Our data suggest that ColA forms dimers upon membrane insertion, thus explaining previously reported pore diameters of about 1 nm, which are unlikely to be formed by a single colicin A monomer.
authors.affiliation: Department of Physics, University of Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany. jklare@uos.de.
authors.forename: S
authors.initials: S
authors.lastname: Dunkel
authors.forename: L P
authors.initials: LP
authors.lastname: Pulagam
authors.forename: H-J
authors.initials: HJ
authors.lastname: Steinhoff
authors.forename: J P
authors.initials: JP
authors.lastname: Klare
mesh_terms: D003087:Colicins / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D004926:Escherichia coli / Q000737:chemistry* / Q000166:cytology; D008958:Models, Molecular; D055503:Protein Multimerization; D013113:Spin Labels
chemical_list: D003087:Colicins; D013113:Spin Labels