title: Membrane topology and functional importance of the periplasmic region of ABC transporter LolCDE.
abstract: The LolCDE complex is an ATP-binding cassette transporter that mediates the release of newly synthesized lipoproteins from the cytoplasmic membrane of gram-negative bacteria, which results in the initiation of outer-membrane sorting of lipoproteins through the Lol pathway. LolCDE is composed of one copy each of membrane subunits LolC and LolE, and two copies of nucleotide-binding subunit LolD. In this study, we examined the membrane topology of LolC and LolE by PhoA fusion analysis. Both LolC and LolE were found to have four transmembrane segments with a large periplasmic loop exposed to the periplasm. Despite similarities in sequence and topology, the accessibility of a sulfhydryl reagent to Cys introduced into the periplasmic loop suggested that the structure of the periplasmic region differs between LolC and LolE. Inhibition of the release of lipoproteins by the sulfhydryl reagent supported a previous proposal that LolC and LolE have distinct functions.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Yasuda
authors.forename: Asako
authors.initials: A
authors.lastname: Iguchi-Yokoyama
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Matsuyama
authors.forename: Hajime
authors.initials: H
authors.lastname: Tokuda
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Narita
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008074:Lipoproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D019897:Periplasm / Q000737:chemistry / Q000378:metabolism*; D013451:Sulfonic Acids / Q000737:chemistry / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D029968:Escherichia coli Proteins; D008074:Lipoproteins; C407982:LolC protein, E coli; C407984:LolE protein, E coli; D013451:Sulfonic Acids; D003545:Cysteine