||Structure of a Bacterial ABC Transporter Involved in the Import of an Acidic Polysaccharide Alginate
Maruyama, Yukie ,
Itoh, Takafumi ,
Kaneko, Ai ,
Nishitani, Yu ,
Mikami, Bunzo ,
Hashimoto, WataruMurata, Kousaku
1654 , 2015-07-30 , Elsevier B.V.
細菌の大規模改変を可能にする新技術の確立 -巨大分子輸送ABCトランスポーターの全構造と輸送機構を解明-. 京都大学プレスリリース. 2015-07-31.
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.