1wvg

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Structure of CDP-D-glucose 4,6-dehydratase from Salmonella typhi

Overview

Tyvelose is a unique 3,6-dideoxyhexose found in the O antigens of some, pathogenic species of Yersinia and Salmonella. It is produced via a, complex biochemical pathway that employs CDP-D-glucose as the starting, ligand. CDP-D-glucose 4,6-dehydratase catalyzes the first irreversible, step in the synthesis of this 3,6-dideoxysugar by converting CDP-D-glucose, to CDP-4-keto-6-deoxyglucose via an NAD+ -dependent intramolecular, oxidation-reduction reaction. Here, the cloning, protein purification and, X-ray crystallographic analysis of CDP-D-glucose 4,6-dehydratase from, Salmonella typhi complexed with the substrate analog CDP-D-xylose are, described. Each subunit of the tetrameric enzyme folds into two domains., The N-terminal region contains a Rossmann fold and provides the platform, for NAD(H) binding. The C-terminal motif is primarily composed of, alpha-helices and houses the binding pocket for the CDP portion of the, CDP-D-xylose ligand. The xylose moiety extends into the active-site cleft, that is located between the two domains. Key residues involved in, anchoring the sugar group to the protein include Ser134, Tyr159, Asn197, and Arg208. Strikingly, Ser134 O gamma and Tyr159 O eta sit within 2.9 A, of the 4'-hydroxyl group of xylose. Additionally, the side chains of, Asp135 and Lys136 are located at 3.5 and 3.2 A, respectively, from C-5 of, xylose. In the structurally related dTDP-D-glucose 4,6-dehydratase, the, Asp/Lys pair is replaced with an Asp/Glu couple. On the basis of this, investigation, it can be speculated that Tyr159 serves as the catalytic, base to abstract the 4'-hydroxyl proton from the sugar and that Asp135 and, Lys136 play critical roles in the subsequent dehydration step that leads, to the final product.

About this Structure

1WVG is a Single protein structure of sequence from Salmonella enterica subsp. enterica serovar typhi with APR and CXY as ligands. Active as CDP-glucose 4,6-dehydratase, with EC number 4.2.1.45 Full crystallographic information is available from OCA.

Reference

Structure of CDP-D-glucose 4,6-dehydratase from Salmonella typhi complexed with CDP-D-xylose., Koropatkin NM, Holden HM, Acta Crystallogr D Biol Crystallogr. 2005 Apr;61(Pt 4):365-73. Epub 2005, Mar 24. PMID:15805590

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