title: Evidence for energy-dependent transposition of core lipopolysaccharide across the inner membrane of Salmonella typhimurium.
abstract: The uncoupler 2,4-dinitrophenol blocks the final step of lipopolysaccharide assembly--transfer of O antigen from undecaprenyl pyrophosphate to core lipopolysaccharide--in intact Salmonella typhimurium but not in isolated membrane fractions. The O-antigen ligase enzyme is not inhibited by dinitrophenol in vitro, and core lipopolysaccharide synthesized in the presence of uncoupler in vivo is functional as acceptor of O antigen in vitro. The evidence strongly suggests that maintenance of proton motive force is required for transmembrane transposition of core lipopolysaccharide to the active site of O-antigen ligase at the periplasmic face of the inner membrane.
authors.affiliation: Department of Microbiology, University of Connecticut Health Center, Farmington 06030.
authors.forename: B C
authors.initials: BC
authors.lastname: McGrath
authors.forename: M J
authors.initials: MJ
authors.lastname: Osborn
mesh_terms: D000942:Antigens, Bacterial / Q000096:biosynthesis*; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism; D004140:Dinitrophenols / Q000494:pharmacology; D004734:Energy Metabolism / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008025:Ligases / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism*; D008564:Membrane Potentials; D019081:O Antigens; D012486:Salmonella typhimurium / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*
chemical_list: D000942:Antigens, Bacterial; D004140:Dinitrophenols; D008070:Lipopolysaccharides; D019081:O Antigens; D008025:Ligases