1ZAL

Fructose-1,6-bisphosphate aldolase from rabbit muscle in complex with partially disordered tagatose-1,6-bisphosphate, a weak competitive inhibitor

Summary for 1ZAL

• Entry DOI: 10.2210/pdb1zal/pdb
• Related: 1ZAH 1ZAI 1ZAJ
• Descriptor: Fructose-bisphosphate aldolase A, PHOSPHATE ION (3 entities in total)
• Functional Keywords: aldolase, weak competitive inhibitor, non covalent complex, tagatose-1, 6-bisphosphate, lyase
• Biological source: Oryctolagus cuniculus (rabbit)
• Cellular location: Cytoplasm, myofibril, sarcomere, I band : P00883
• Total number of polymer chains: 4
• Total formula weight: 157814.46

Authors

St-Jean, M.,Lafrance-Vanasse, J.,Liotard, B.,Sygusch, J. (deposition date: 2005-04-06, release date: 2005-05-10, Last modification date: 2023-08-23)

Primary citation

St-Jean, M.,Lafrance-Vanasse, J.,Liotard, B.,Sygusch, J.
High Resolution Reaction Intermediates of Rabbit Muscle Fructose-1,6-bisphosphate Aldolase: substrate cleavage and induced fit.
J.Biol.Chem., 280:27262-27270, 2005

PubMed Abstract: 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.

PubMed: 15870069
DOI: 10.1074/jbc.M502413200

Experimental method

X-RAY DIFFRACTION (1.89 Å)