2csc

Structure of ternary complexes of CITRATE SYNTHASE WITH D-AND L-MALATE: mechanistic implications

spinqualitylabelsall models 2csc, resolution 1.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2csc is a 1 chain structure with sequence from Gallus gallus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CMC, MLT NonStd Res: UNK Activity: Citrate (Si)-synthase, with EC number 2.3.3.1 Resources: FirstGlance, OCA, RCSB, PDBsum Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed The structures of four isomorphous crystals of ternary complexes of chicken heart citrate synthase with D- or L-malate and acetyl coenzyme A or carboxymethyl coenzyme A have been determined by X-ray crystallography and fully refined at 1.9-A resolution. The structures show that both L-malate and D-malate bind in a very similar way in the presence of acetylCoA and that the enzyme conformation is "closed". Hydrogen bond geometry is suggested to account for the difference in binding constants of the two stereoisomers. The structures suggest that steric hindrance can account for the observation that proton exchange of acetyl coenzyme A with solvent is catalyzed by citrate synthase in the presence of L-malate but not D-malate. The ternary complexes with malate reveal the mode of binding of the substrate acetylCoA in the ground state. The carbonyl oxygen of the acetyl group is hydrogen bonded to a water molecule and to histidine 274, allowing unambiguous identification of the orientation of this group. The structures support the hypothesis that carboxymethyl coenzyme A is a transition-state analogue for the enolization step of the reaction (Bayer et al., 1981) and additionally support proposed mechanisms for the condensation reaction (Karpusas et al., 1990; Alter et al., 1990). 1.9-A structures of ternary complexes of citrate synthase with D- and L-malate: mechanistic implications.,Karpusas M, Holland D, Remington SJ Biochemistry. 1991 Jun 18;30(24):6024-31. PMID:2043640 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Citrate Synthase

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