1owc

Three Dimensional Structure Analysis Of The R109L Variant of the Type II Citrate Synthase From E. Coli

spinqualitylabelsall models 1owc, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1owc is a 2 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.2Å Ligands: SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CISY_ECOLI 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 citrate synthase of Escherichia coli is an example of a Type II citrate synthase, a hexamer that is subject to allosteric inhibition by NADH. In previous crystallographic work, we defined the NADH binding sites, identifying nine amino acids whose side chains were proposed to make hydrogen bonds with the NADH molecule. Here, we describe the functional properties of nine sequence variants, in which these have been replaced by nonbonding residues. All of the variants show some changes in NADH binding and inhibition and small but significant changes in kinetic parameters for catalysis. In three cases, Y145A, R163L, and K167A, NADH inhibition has become extremely weak. We have used nanospray/time-of-flight mass spectrometry, under non-denaturing conditions, to show that two of these, R163L and K167A, do not form hexamers in response to NADH binding, unlike the wild type enzyme. One variant, R109L, shows tighter NADH binding. We have crystallized this variant and determined its structure, with and without bound NADH. Unexpectedly, the greatest structural changes in the R109L variant are in two regions outside the NADH binding site, both of which, in wild type citrate synthase, have unusually high mobilities as measured by crystallographic thermal factors. In the R109L variant, both regions (residues 260 -311 and 316-342) are much less mobile and have rearranged significantly. We argue that these two regions are elements in the path of communication between the NADH binding sites and the active sites and are centrally involved in the regulatory conformational change in E. coli citrate synthase. Probing the roles of key residues in the unique regulatory NADH binding site of type II citrate synthase of Escherichia coli.,Stokell DJ, Donald LJ, Maurus R, Nguyen NT, Sadler G, Choudhary K, Hultin PG, Brayer GD, Duckworth HW J Biol Chem. 2003 Sep 12;278(37):35435-43. Epub 2003 Jun 23. PMID:12824188 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Citrate Synthase 3D structures

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