1orr
From Proteopedia
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Crystal Structure of CDP-Tyvelose 2-Epimerase complexed with NAD and CDP
Overview
Tyvelose epimerase catalyzes the last step in the biosynthesis of tyvelose, by converting CDP-d-paratose to CDP-d-tyvelose. This unusual, 3,6-dideoxyhexose occurs in the O-antigens of some types of Gram-negative, bacteria. Here we describe the cloning, protein purification, and, high-resolution x-ray crystallographic analysis of tyvelose epimerase from, Salmonella typhi complexed with CDP. The enzyme from S. typhi is a, homotetramer with each subunit containing 339 amino acid residues and a, tightly bound NAD+ cofactor. The quaternary structure of the enzyme, displays 222 symmetry and can be aptly described as a dimer of dimers., Each subunit folds into two distinct lobes: the N-terminal motif, responsible for NAD+ binding and the C-terminal region that harbors the, binding site for CDP. The analysis described here demonstrates that, tyvelose epimerase belongs to the short-chain dehydrogenase/reductase, superfamily of enzymes. Indeed, its active site is reminiscent to that, observed for UDP-galactose 4-epimerase, an enzyme that plays a key role in, galactose metabolism. Unlike UDP-galactose 4-epimerase where the, conversion of configuration occurs about C-4 of the UDP-glucose or, UDP-galactose substrates, in the reaction catalyzed by tyvelose epimerase, the inversion of stereochemistry occurs at C-2. On the basis of the, observed binding mode for CDP, it is possible to predict the manner in, which the substrate, CDP-paratose, and the product, CDP-tyvelose, might be, accommodated within the active site of tyvelose epimerase.
About this Structure
1ORR is a Single protein structure of sequence from Salmonella typhi with NAD and CDP as ligands. Full crystallographic information is available from OCA.
Reference
High resolution x-ray structure of tyvelose epimerase from Salmonella typhi., Koropatkin NM, Liu HW, Holden HM, J Biol Chem. 2003 Jun 6;278(23):20874-81. Epub 2003 Mar 17. PMID:12642575
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