1x8f
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Crystal Structure Of apo-Kdo8P Synthase
OverviewOverview
The enzyme 3-deoxy-D-manno-2-octulosonate-8-phosphate synthase (KDO8PS), catalyses the condensation of arabinose 5-phosphate (A5P) and phosphoenol, pyruvate (PEP) to obtain 3-deoxy-D-manno-2-octulosonate-8-phosphate, (KDO8P). We have elucidated initial modes of ligand binding in KDO8PS, binary complexes by X-ray crystallography. Structures of the apo-enzyme, and of binary complexes with the substrate PEP, the product KDO8P and the, catalytically inactive 1-deoxy analog of arabinose 5-phosphate (1dA5P), were obtained. The KDO8PS active site resembles an irregular funnel with, positive electrostatic potential situated at the bottom of the PEP-binding, sub-site, which is the primary attractive force towards negatively charged, phosphate moieties of all ligands. The structures of the ligand-free, apo-KDO8PS and the binary complex with the product KDO8P visualize for the, first time the role of His202 as an active-site gate. Examination of the, crystal structures of KDO8PS with the KDO8P or 1dA5P shows these ligands, bound to the enzyme in the PEP-binding sub-site, and not as expected to, the A5P sub-site. Taken together, the structures presented here strengthen, earlier evidence that this enzyme functions predominantly through, positional catalysis, map out the roles of active-site residues and, provide evidence that explains the total lack of catalytic reversibility.
About this StructureAbout this Structure
1X8F is a Single protein structure of sequence from Escherichia coli. Active as 3-deoxy-8-phosphooctulonate synthase, with EC number 2.5.1.55 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures of Escherichia coli KDO8P synthase complexes reveal the source of catalytic irreversibility., Vainer R, Belakhov V, Rabkin E, Baasov T, Adir N, J Mol Biol. 2005 Aug 19;351(3):641-52. PMID:16023668
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