title: Structure of a Bacterial ABC Transporter Involved in the Import of an Acidic Polysaccharide Alginate.
abstract: The acidic polysaccharide alginate represents a promising marine biomass for the microbial production of biofuels, although the molecular and structural characteristics of alginate transporters remain to be clarified. In Sphingomonas sp. A1, the ATP-binding cassette transporter AlgM1M2SS is responsible for the import of alginate across the cytoplasmic membrane. Here, we present the substrate-transport characteristics and quaternary structure of AlgM1M2SS. The addition of poly- or oligoalginate enhanced the ATPase activity of reconstituted AlgM1M2SS coupled with one of the periplasmic solute-binding proteins, AlgQ1 or AlgQ2. External fluorescence-labeled oligoalginates were specifically imported into AlgM1M2SS-containing proteoliposomes in the presence of AlgQ2, ATP, and Mg(2+). The crystal structure of AlgQ2-bound AlgM1M2SS adopts an inward-facing conformation. The interaction between AlgQ2 and AlgM1M2SS induces the formation of an alginate-binding tunnel-like structure accessible to the solvent. The translocation route inside the transmembrane domains contains charged residues suitable for the import of acidic saccharides.
authors.affiliation: Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Yukie
authors.initials: Y
authors.lastname: Maruyama
authors.affiliation: Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Itoh
authors.affiliation: Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Kaneko
authors.affiliation: Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Nishitani
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Bunzo
authors.initials: B
authors.lastname: Mikami
authors.affiliation: Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan. Electronic address: whasimot@kais.kyoto-u.ac.jp.
authors.forename: Wataru
authors.initials: W
authors.lastname: Hashimoto
authors.affiliation: Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan. Electronic address: k-murata@lif.setsunan.ac.jp.
authors.forename: Kousaku
authors.initials: K
authors.lastname: Murata
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000464:Alginates / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D020723:Glucuronic Acid / Q000378:metabolism; D006603:Hexuronic Acids / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D020578:Sphingomonas / Q000737:chemistry / Q000201:enzymology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D000464:Alginates; D001426:Bacterial Proteins; D006603:Hexuronic Acids; D020723:Glucuronic Acid; D000255:Adenosine Triphosphate; D008274:Magnesium