title: Pore formation and function of phosphoporin PhoE of Escherichia coli are determined by the core sugar moiety of lipopolysaccharide.
abstract: The lipid matrix of the outer membrane of Gram-negative bacteria is an asymmetric bilayer composed of a phospholipid inner leaflet and a lipopolysaccharide outer leaflet. Incorporated into this lipid matrix are, among other macromolecules, the porins, which have a sieve-like function for the transport or exclusion of hydrophilic substances. It is known that a reduced amount of porins is found in the outer membrane of rough mutants as compared with wild-type bacteria. This observation was discussed to be caused by a reduced number of insertion sites in the former. We performed electrical measurements on reconstituted planar bilayers composed of lipopolysaccharide on one side and a phospholipid mixture on the other side using lipopolysaccharide from various rough mutant strains of Salmonella enterica serovar Minnesota. We found that pore formation by PhoE trimers that were added to the phospholipid side of the bilayers increased with the increasing length of the lipopolysaccharide core sugar moiety. These results allow us to conclude that the length of the sugar moiety of lipopolysaccharide is the parameter governing pore formation and that no particular insertion sites are required. Furthermore, we found that the voltage gating of the porin channels is strongly dependent on the composition of the lipid matrix.
authors.affiliation: Center for Medicine and Biosciences, Department of Immunochemistry and Biochemical Microbiology, Research Center Borstel, Parkallee 1-40, D-23845 Borstel, Germany.
authors.forename: Sven O
authors.initials: SO
authors.lastname: Hagge
authors.forename: Hans
authors.initials: H
authors.lastname: de Cock
authors.forename: Thomas
authors.initials: T
authors.lastname: Gutsmann
authors.forename: Frank
authors.initials: F
authors.lastname: Beckers
authors.forename: Ulrich
authors.initials: U
authors.lastname: Seydel
authors.forename: Andre
authors.initials: A
authors.lastname: Wiese
mesh_terms: D029968:Escherichia coli Proteins / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D008070:Lipopolysaccharides / Q000737:chemistry*; D008274:Magnesium / Q000494:pharmacology; D018272:Porins / Q000737:chemistry* / Q000502:physiology
chemical_list: D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D008070:Lipopolysaccharides; D018272:Porins; C082922:PhoE protein, E coli; D008274:Magnesium