4bjh | pdb_00004bjh

Crystal Structure of the Aquifex Reactor Complex Formed by Dihydroorotase (H180A, H232A) with Dihydroorotate and Aspartate Transcarbamoylase with N-(phosphonacetyl)-L-aspartate (PALA)

spinqualitylabelsall models 4bjh, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4bjh is a 2 chain structure with sequence from Aquifex aeolicus. 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: BA, DOR, EDO, PAL, PO4, ZN Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function PYRC_AQUAE Publication Abstract from PubMed BACKGROUND: Dihydroorotase (DHO) is a zinc metalloenzyme, although the number of active site zinc ions has been controversial. E. coli DHO was initially thought to have a mononuclear metal center, but the subsequent X-ray structure clearly showed two zinc ions, alpha and beta, at the catalytic site. Aquifex aeolicus DHO, is a dodecamer comprised of six DHO and six aspartate transcarbamoylase (ATC) subunits. The isolated DHO monomer, which lacks catalytic activity, has an intact alpha-site and conserved beta-site ligands, but the geometry of the second metal binding site is completely disrupted. However, the putative beta-site is restored when the complex with ATC is formed and DHO activity is regained. Nevertheless, the X-ray structure of the complex revealed a single zinc ion at the active site. The structure of DHO from the pathogenic organism, S. aureus showed that it also has a single active site metal ion. RESULTS: Zinc analysis showed that the enzyme has one zinc/DHO subunit and the addition of excess metal ion did not stimulate catalytic activity, nor alter the kinetic parameters. The metal free apoenzyme was inactive, but the full activity was restored upon the addition of one equivalent of Zn2+ or Co2+. Moreover, deletion of the beta-site by replacing the His180 and His232 with alanine had no effect on catalysis in the presence or absence of excess zinc. The 2.2 A structure of the double mutant confirmed that the beta-site was eliminated but that the active site remained otherwise intact. CONCLUSIONS: Thus, kinetically competent A. aeolicus DHO has a mononuclear metal center. In contrast, elimination of the putative second metal binding site in amidohydrolyases with a binuclear metal center, resulted in the abolition of catalytic activity. The number of active site metal ions may be a consideration in the design of inhibitors that selectively target either the mononuclear or binuclear enzymes. The mononuclear metal center of type-I dihydroorotase from aquifex aeolicus.,Edwards BF, Fernando R, Martin PD, Grimley E, Cordes M, Vaishnav A, Brunzelle JS, Evans HG, Evans DR BMC Biochem. 2013 Dec 9;14(1):36. PMID:24314009 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Aspartate carbamoyltransferase 3D structures Dihydroorotase 3D structures

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