1zai
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| , resolution 1.76Å | |||||||
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| Ligands: | |||||||
| Gene: | ALDOA (Oryctolagus cuniculus) | ||||||
| Activity: | Fructose-bisphosphate aldolase, with EC number 4.1.2.13 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Fructose-1,6-bisphosphate Schiff base intermediate in FBP aldolase from rabbit muscle
OverviewOverview
Crystal structures were determined to 1.8 A resolution of the glycolytic enzyme fructose-1,6-bis(phosphate) aldolase trapped in complex with its substrate and a competitive inhibitor, mannitol-1,6-bis(phosphate). The enzyme substrate complex corresponded to the postulated Schiff base intermediate and has reaction geometry consistent with incipient C3-C4 bond cleavage catalyzed Glu-187, which is adjacent by to the Schiff base forming Lys-229. Atom arrangement about the cleaved bond in the reaction intermediate mimics a pericyclic transition state occurring in nonenzymatic aldol condensations. Lys-146 hydrogen-bonds the substrate C4 hydroxyl and assists substrate cleavage by stabilizing the developing negative charge on the C4 hydroxyl during proton abstraction. Mannitol-1,6-bis(phosphate) forms a noncovalent complex in the active site whose binding geometry mimics the covalent carbinolamine precursor. Glu-187 hydrogen-bonds the C2 hydroxyl of the inhibitor in the enzyme complex, substantiating a proton transfer role by Glu-187 in catalyzing the conversion of the carbinolamine intermediate to Schiff base. Modeling of the acyclic substrate configuration into the active site shows Glu-187, in acid form, hydrogen-bonding both substrate C2 carbonyl and C4 hydroxyl, thereby aligning the substrate ketose for nucleophilic attack by Lys-229. The multifunctional role of Glu-187 epitomizes a canonical mechanistic feature conserved in Schiff base-forming aldolases catalyzing carbohydrate metabolism. Trapping of tagatose-1,6-bis(phosphate), a diastereoisomer of fructose 1,6-bis(phosphate), displayed stereospecific discrimination and reduced ketohexose binding specificity. Each ligand induces homologous conformational changes in two adjacent alpha-helical regions that promote phosphate binding in the active site.
About this StructureAbout this Structure
1ZAI is a Single protein structure of sequence from Oryctolagus cuniculus. Full crystallographic information is available from OCA.
ReferenceReference
High resolution reaction intermediates of rabbit muscle fructose-1,6-bisphosphate aldolase: substrate cleavage and induced fit., St-Jean M, Lafrance-Vanasse J, Liotard B, Sygusch J, J Biol Chem. 2005 Jul 22;280(29):27262-70. Epub 2005 May 3. PMID:15870069
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