1X6U: Kdo8p Synthase In It's Binary Complex With The Product Kdo8p

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.
PDB ID: 1X6UDownload
MMDB ID: 34176
PDB Deposition Date: 2004/8/12
Updated in MMDB: 2012/12
Experimental Method:
x-ray diffraction
Resolution: 2.7  Å
Source Organism:
Similar Structures:
Biological Unit for 1X6U: tetrameric; determined by author and by software (PISA,PQS)
Molecular Components in 1X6U
Label Count Molecule
Proteins (4 molecules)
2-dehydro-3-deoxyphosphooctonate Aldolase(Gene symbol: kdsA)
Molecule annotation
Chemicals (4 molecules)
* Click molecule labels to explore molecular sequence information.

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