1rpn
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(New page: 200px<br /><applet load="1rpn" size="450" color="white" frame="true" align="right" spinBox="true" caption="1rpn, resolution 2.15Å" /> '''Crystal Structure of...)
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Revision as of 23:39, 20 November 2007
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Crystal Structure of GDP-D-mannose 4,6-dehydratase in complexes with GDP and NADPH
Overview
d-Rhamnose is a rare 6-deoxy monosaccharide primarily found in the, lipopolysaccharide of pathogenic bacteria, where it is involved in, host-bacterium interactions and the establishment of infection. The, biosynthesis of d-rhamnose proceeds through the conversion of, GDP-d-mannose by GDP-d-mannose 4,6-dehydratase (GMD) to, GDP-4-keto-6-deoxymannose, which is subsequently reduced to GDP-d-rhamnose, by a reductase. We have determined the crystal structure of GMD from, Pseudomonas aeruginosa in complex with NADPH and GDP. GMD belongs to the, NDP-sugar modifying subfamily of the short-chain dehydrogenase/reductase, (SDR) enzymes, all of which exhibit bidomain structures and a conserved, catalytic triad (Tyr-XXX-Lys and Ser/Thr). Although most members of this, enzyme subfamily display homodimeric structures, this bacterial GMD forms, a tetramer in the same fashion as the plant MUR1 from Arabidopsis, thaliana. The cofactor binding sites are adjoined across the tetramer, interface, which brings the adenosyl phosphate moieties of the adjacent, NADPH molecules to within 7 A of each other. A short peptide segment, (Arg35-Arg43) stretches into the neighboring monomer, making not only, protein-protein interactions but also hydrogen bonding interactions with, the neighboring cofactor. The interface hydrogen bonds made by the, Arg35-Arg43 segment are generally conserved in GMD and MUR1, and the, interacting residues are highly conserved among the sequences of bacterial, and eukaryotic GMDs. Outside of the Arg35-Arg43 segment, residues involved, in tetrameric contacts are also quite conserved across different species., These observations suggest that a tetramer is the preferred, and perhaps, functionally relevant, oligomeric state for most bacterial and eukaryotic, GMDs.
About this Structure
1RPN is a Single protein structure of sequence from Pseudomonas aeruginosa with NDP and GDP as ligands. Active as GDP-mannose 4,6-dehydratase, with EC number 4.2.1.47 Full crystallographic information is available from OCA.
Reference
Crystal structure of a tetrameric GDP-D-mannose 4,6-dehydratase from a bacterial GDP-D-rhamnose biosynthetic pathway., Webb NA, Mulichak AM, Lam JS, Rocchetta HL, Garavito RM, Protein Sci. 2004 Feb;13(2):529-39. PMID:14739333
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