title: Transport of ferric-aerobactin into the periplasm and cytoplasm of Escherichia coli K12: role of envelope-associated proteins and effect of endogenous siderophores.
abstract: Purified [14C]aerobactin, supplied exogenously to non-growing bacteria, was translocated via the periplasm into the cytoplasm of Escherichia coli K12 strains expressing the aerobactin receptor protein IutA. No significant uptake was observed into either compartment of strains lacking the iutA gene or specifically defective in tonB. Uptake into both compartments was markedly reduced, but not abolished, in an exb mutant. Accumulation of [14C]aerobactin in the periplasm of fhuD, fhuB or fhuC mutant strains was not significantly lower than in the wild-type strain, but entry into the cytoplasm was greatly reduced in all cases. Uptake of aerobactin by strains wild-type for all transport functions occurred most efficiently in strains either lacking or specifically defective in the genetic determinants for aerobactin biosynthesis; significantly lower levels of exogenous 14C-labelled siderophore were observed in both compartments of strains producing aerobactin. Aerobactin-mediated 59Fe uptake, however, was not inhibited by the presence of endogenous aerobactin. Endogenous enterochelin did not affect aerobactin uptake.
authors.affiliation: Department of Genetics, University of Leicester, UK.
authors.forename: K G
authors.initials: KG
authors.lastname: Wooldridge
authors.forename: J A
authors.initials: JA
authors.lastname: Morrissey
authors.forename: P H
authors.initials: PH
authors.lastname: Williams
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D005290:Ferric Compounds / Q000378:metabolism; D006877:Hydroxamic Acids / Q000302:isolation & purification / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D011971:Receptors, Immunologic / Q000378:metabolism; D017262:Siderophores
chemical_list: D001425:Bacterial Outer Membrane Proteins; D005290:Ferric Compounds; D006877:Hydroxamic Acids; D007502:Iron Chelating Agents; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D017262:Siderophores; C034506:aerobactin receptor; C031819:aerobactin