3oo7 | pdb_00003oo7

Crystal structures and biochemical characterization of the bacterial solute receptor AcbH reveal an unprecedented exclusive substrate preference for b-D-galactopyranose

spinqualitylabelsall models 3oo7, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3oo7 is a 1 chain structure with sequence from Acts5. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: GOL, SO4 Related: 3oo6, 3oo8, 3oo9, 3ooa Gene: AcbH (ACTS5) Resources: FirstGlance, OCA, RCSB, PDBsum Publication Abstract from PubMed Solute receptors (binding proteins) are indispensable components of canonical ATP-binding cassette importers in prokaryotes. Here, we report on the characterization and crystal structures in the closed and open conformations of AcbH, the solute receptor of the putative carbohydrate transporter AcbFG which is encoded in the acarbose (acarviosyl-1,4-maltose) biosynthetic gene cluster from Actinoplanes sp. SE50/110. Binding assays identified AcbH as a high-affinity monosaccharide-binding protein with a dissociation constant (K(d)) for beta-d-galactopyranose of 9.8+/-1.0 nM. Neither galactose-containing di- and trisaccharides, such as lactose and raffinose, nor monosaccharides including d-galacturonic acid, l-arabinose, d-xylose and l-rhamnose competed with [(1)(4)C]galactose for binding to AcbH. Moreover, AcbH does not bind d-glucose, which is a common property of all but one d-galactose-binding proteins characterized to date. Strikingly, determination of the X-ray structure revealed that AcbH is structurally homologous to maltose-binding proteins rather than to glucose-binding proteins. Two helices are inserted in the substrate-binding pocket, which reduces the cavity size and allows the exclusive binding of monosaccharides, specifically beta-d-galactopyranose, in the (4)C(1) conformation. Site-directed mutagenesis of three residues from the binding pocket (Arg82, Asp361 and Arg362) that interact with the axially oriented O4-H hydroxyl of the bound galactopyranose and subsequent functional analysis indicated that these residues are crucial for galactose binding. To our knowledge, this is the first report of the tertiary structure of a solute receptor with exclusive affinity for beta-d-galactopyranose. The putative role of a galactose import system in the context of acarbose metabolism in Actinoplanes sp. is discussed. Crystal structures of the bacterial solute receptor AcbH displaying an exclusive substrate preference for beta-D-galactopyranose.,Licht A, Bulut H, Scheffel F, Daumke O, Wehmeier UF, Saenger W, Schneider E, Vahedi-Faridi A J Mol Biol. 2011 Feb 11;406(1):92-105. Epub 2010 Dec 17. PMID:21168419 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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