The periplasmic binding component of ABC transport systems specific for cyclo/maltodextrin; possess the type 2 periplasmic binding fold.
This group includes the periplasmic cyclo/maltodextrin-binding protein of Thermoactinomyces vulgaris ATP-binding cassette transporter and related proteins. Cyclodextrins are a family of compounds composed of glucose units connected by 1, 4 glycosidic linkages to form a series of oligosaccharide rings, and their cavity is hydrophibic which allows cyclodextrins to accomodate hydrophobic molecules/moieties in the cavity. Members of this group belong to the type 2 periplasmic-binding fold superfamily. PBP2 is comprised of two globular subdomains connected by a flexible hinge and bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap. The majority of PBP2 proteins function in the uptake of small soluble substrates in eubacteria and archaea. After binding their specific ligand with high affinity, they can interact with a cognate membrane transport complex comprised of two integral membrane domains and two cytoplasmically located ATPase domains. This interaction triggers the ligand translocation across the cytoplasmic membrane energized by ATP hydrolysis.
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