4jad | pdb_00004jad

STRUCTURAL DETERMINATION OF THE A50T:S279G:S280K:V281K:K282E:H283N VARIANT OF CITRATE SYNTHASE from E. COLI

spinqualitylabelsall models 4jad, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4jad is a 2 chain structure with sequence from Escherichia coli K-12. This structure supersedes the now removed PDB entry 3l96. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CISY_ECOLI Publication Abstract from PubMed The citrate synthase (CS) of Escherichia coli is an allosteric hexameric enzyme specifically inhibited by NADH. The crystal structure of wild type (WT) E. coli CS, determined by us previously, has no substrates bound, and part of the active site is in a highly mobile region that is shifted from the position needed for catalysis. The CS of Acetobacter aceti has a similar structure, but has been successfully crystallized with bound substrates: both oxaloacetic acid (OAA) and an analog of acetyl coenzyme A (AcCoA). We engineered a variant of E. coli CS wherein five amino acids in the mobile region have been replaced by those in the A. aceti sequence. The purified enzyme shows unusual kinetics with a low affinity for both substrates. Although the crystal structure without ligands is very similar to that of the WT enzyme (except in the mutated region), complexes are formed with both substrates and the allosteric inhibitor NADH. The complex with OAA in the active site identifies a novel OAA-binding residue, Arg306, which has no functional counterpart in other known CS-OAA complexes. This structure may represent an intermediate in a multi-step substrate binding process where Arg306 changes roles from OAA binding to AcCoA binding. The second complex has the substrate analog, S-carboxymethyl-coenzyme A, in the allosteric NADH-binding site and the AcCoA site is not formed. Additional CS variants unable to bind adenylates at the allosteric site show that this second complex is not a factor in positive allosteric activation of AcCoA binding. Enzyme-substrate complexes of allosteric citrate synthase: Evidence for a novel intermediate in substrate binding.,Duckworth HW, Nguyen NT, Gao Y, Donald LJ, Maurus R, Ayed A, Bruneau B, Brayer GD Biochim Biophys Acta. 2013 Aug 14. pii: S1570-9639(13)00291-4. doi:, 10.1016/j.bbapap.2013.07.019. PMID:23954305 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Citrate Synthase 3D structures

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