1fqd
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CRYSTAL STRUCTURE OF MALTOTETRAITOL BOUND TO CLOSED-FORM MALTODEXTRIN BINDING PROTEIN
OverviewOverview
The structure of the maltodextrin or maltose-binding protein, an initial, receptor for bacterial ABC-type active transport and chemotaxis, consists, of two globular domains that are separated by a groove wherein the ligand, is bound and enclosed by an inter-domain rotation. Here, we report the, determination of the crystal structures of the protein complexed with, reduced maltooligosaccharides (maltotriitol and maltotetraitol) in both, the "closed" and "open" forms. Although these modified sugars bind to the, receptor, they are not transported by the wild-type transporter. In the, closed structures, the reduced sugars are buried in the groove and bound, by both domains, one domain mainly by hydrogen-bonding interactions and, the other domain primarily by non-polar interactions with aromatic, side-chains. In the open structures, which abrogate both cellular, activities of active transport and chemotaxis because of the large, separation between the two domains, the sugars are bound almost, exclusively to the domain rich in aromatic residues. The binding site for, the open chain glucitol residue extends to a subsite that is distinct from, those for the glucose residues that were uncovered in prior structural, studies of the binding of active linear maltooligosaccharides. Occupation, of this subsite may also account for the inability of the reduced, oligosaccharides to be transported. The structures reported here, combined, with those previously determined for several other complexes with active, oligosaccharides in the closed form and with cyclodextrin in the open, form, revealed at least four distinct modes of ligand binding but with, only one being functionally active. This versatility reflects the, flexibility of the protein, from very large motions of interdomain, rotation to more localized side-chain conformational changes, and, adaptation by the oligosaccharides as well.
About this StructureAbout this Structure
1FQD is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of the maltodextrin/maltose-binding protein complexed with reduced oligosaccharides: flexibility of tertiary structure and ligand binding., Duan X, Hall JA, Nikaido H, Quiocho FA, J Mol Biol. 2001 Mar 9;306(5):1115-26. PMID:11237621
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