title: Iron(III) hydroxamate transport in Escherichia coli K-12: FhuB-mediated membrane association of the FhuC protein and negative complementation of fhuC mutants.
abstract: Iron(III) hydroxamate transport across the cytoplasmic membrane is catalyzed by the very hydrophobic FhuB protein and the membrane-associated FhuC protein, which contains typical ATP-binding domains. Interaction between the two proteins was demonstrated by immunoelectron microscopy with anti-FhuC antibodies, which showed FhuB-mediated association of FhuC with the cytoplasmic membrane. In addition, inactive FhuC derivatives carrying single amino acid replacements in the ATP-binding domains suppressed wild-type FhuC transport activity, which arose either from displacement of active FhuC from FhuB by the mutated FhuC derivatives or from the formation of mixed inactive FhuC multimers between wild-type and mutated FhuC proteins. Inactive FhuC derivatives containing internal deletions and insertions showed no phenotypic suppression, indicating conformational alterations that rendered the FhuC derivatives unable to displace wild-type FhuC. It is concluded that the physical interaction between FhuC and FhuB implies a coordinate activity of both proteins in the transport of iron(III) hydroxamates through the cytoplasmic membrane.
authors.affiliation: Mikrobiologie II, Universität Tübingen, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Schultz-Hauser
authors.forename: W
authors.initials: W
authors.lastname: Köster
authors.forename: H
authors.initials: H
authors.lastname: Schwarz
authors.forename: V
authors.initials: V
authors.lastname: Braun
mesh_terms: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002451:Cell Compartmentation; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005290:Ferric Compounds / Q000378:metabolism*; D005816:Genetic Complementation Test; D006877:Hydroxamic Acids / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D033902:Periplasmic Binding Proteins
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D005290:Ferric Compounds; C066629:FhuC protein, E coli; D006877:Hydroxamic Acids; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009838:Oligodeoxyribonucleotides; D033902:Periplasmic Binding Proteins; C069968:fhuB protein, E coli