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Publication Abstract from PubMedThe 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 Mg2+. 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. Structure of a Bacterial ABC Transporter Involved in the Import of an Acidic Polysaccharide Alginate.,Maruyama Y, Itoh T, Kaneko A, Nishitani Y, Mikami B, Hashimoto W, Murata K Structure. 2015 Jul 21. pii: S0969-2126(15)00274-9. doi:, 10.1016/j.str.2015.06.021. PMID:26235029[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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