title: The voltage-dependent activity of Escherichia coli porins in different planar bilayer reconstitutions.
abstract: Because of conflicting results from differing techniques, the degree of voltage sensitivity of Escherichia coli porins in planar bilayers is still a matter of debate. In order to provide the first comparative study, OmpF porin was purified in three ways; firstly as native outer membrane vesicles, secondly as salt-extracted porin trimers in sodium dodecyl sulphate and thirdly as solubilised trimers extracted with octyl-polyoxyethylene (Octyl-POE). These methods represent the major approaches to porin isolation and purification. All three were reconstituted into Schindler-type bilayers. Detergent-solubilised OmpF was also reconstituted into Montal-Mueller- and Mueller-Rudin-type bilayers. In all cases voltage-dependent closing of OmpF was observed. Octyl-POE-extracted PhoE porin was similarly investigated in all three types of planar bilayer. Two membrane-formation techniques appeared genuinely to alter the voltage sensitivity of the porins they contained. Firstly, porins in membranes formed by the Montal-Mueller technique sometimes showed an increase in voltage sensitivity during the first 30 min after bilayer formation. Secondly, membranes formed by the Mueller-Rudin technique on thick polyethylene septa showed both poor solvent drainage and a significantly reduced porin voltage sensitivity.
authors: European Molecular Biology Laboratory, Heidelberg, FRG.
authors: J H
authors: JH
authors: Lakey
authors: F
authors: F
authors: Pattus
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism / Q000502:physiology*; D008563:Membrane Lipids / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D008722:Methods; D018272:Porins; D011485:Protein Binding
chemical_list: D001425:Bacterial Outer Membrane Proteins; D007473:Ion Channels; D008563:Membrane Lipids; D018272:Porins