title: Export of the siderophore enterobactin in Escherichia coli: involvement of a 43 kDa membrane exporter.
abstract: The enterobactin system for iron transport in Escherichia coli is well characterized with the exception of the mechanism of enterobactin secretion to the extracellular environment. Escherichia coli membrane protein P43, encoded by ybdA in the chromosomal region of genes involved in enterobactin synthesis, shows strong homology to the 12-transmembrane segment major facilitator superfamily of export pumps. A P43-null mutation was created and siderophore nutrition assays, performed with a panel of E. coli strains expressing one or more outer membrane receptors for enterobactin-related compounds, demonstrated that the P43 mutant was unable to secrete enterobactin efficiently. Products released from the mutant strain were identified with thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), revealing that the P43 mutant secretes little, if any, enterobactin, but elevated levels of enterobactin breakdown products 2,3- dihydroxybenzoylserine (DHBS) monomer, dimer, and trimer. These data establish that P43 is a critical component of the E. coli enterobactin secretion machinery and provides a rationale for the designation of the previous genetic locus ybdA as entS to reflect its relevant biological function.
authors.affiliation: Department of Molecular Microbiology and Immunology, University of Missouri-Columbia, Columbia, MO, USA.
authors.forename: Jason L
authors.initials: JL
authors.lastname: Furrer
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Sanders
authors.forename: India G
authors.initials: IG
authors.lastname: Hook-Barnard
authors.forename: Mark A
authors.initials: MA
authors.lastname: McIntosh
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001692:Biological Transport; D002851:Chromatography, High Pressure Liquid; D004758:Enterobactin / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D017433:Protein Structure, Secondary
chemical_list: D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D004758:Enterobactin