3d6n

Crystal Structure of Aquifex Dihydroorotase Activated by Aspartate Transcarbamoylase

spinqualitylabelsall models 3d6n, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3d6n is a 2 chain structure with sequence from "aquifex_aeolicus"_huber_and_stetter_2001 "aquifex aeolicus" huber and stetter 2001. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: FLC, ZN Related: 1xrt, 1xrf Gene: pyrC, aq_806 ("Aquifex aeolicus" Huber and Stetter 2001), pyrB, aq_409 ("Aquifex aeolicus" Huber and Stetter 2001) Activity: Dihydroorotase, with EC number 3.5.2.3 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT 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 In prokaryotes, the first three enzymes in pyrimidine biosynthesis, carbamoyl phosphate synthetase (CPS), aspartate transcarbamoylase (ATC), and dihydroorotase (DHO), are commonly expressed separately and either function independently (Escherichia coli) or associate into multifunctional complexes (Aquifex aeolicus). In mammals the enzymes are expressed as a single polypeptide chain (CAD) in the order CPS-DHO-ATC and associate into a hexamer. This study presents the three-dimensional structure of the noncovalent hexamer of DHO and ATC from the hyperthermophile A. aeolicus at 2.3 A resolution. It is the first structure of any multienzyme complex in pyrimidine biosynthesis and is a possible model for the core of mammalian CAD. The structure has citrate, a near isosteric analogue of carbamoyl aspartate, bound to the active sites of both enzymes. Three active site loops that are intrinsically disordered in the free, inactive DHO are ordered in the complex. The reorganization also changes the peptide bond between Asp153, a ligand of the single zinc atom in DHO, and Gly154, to the rare cis conformation. In the crystal structure, six DHO and six ATC chains form a hollow dodecamer, in which the 12 active sites face an internal reaction chamber that is approximately 60 A in diameter and connected to the cytosol by narrow tunnels. The entrances and the interior of the chamber are both electropositive, which suggests that the architecture of this nanoreactor modifies the kinetics of the bisynthase, not only by steric channeling but also by preferential escape of the product, dihydroorotase, which is less negatively charged than its precursors, carbamoyl phosphate, aspartate, or carbamoyl aspartate. Dihydroorotase from the Hyperthermophile Aquifiex aeolicus Is Activated by Stoichiometric Association with Aspartate Transcarbamoylase and Forms a One-Pot Reactor for Pyrimidine Biosynthesis (dagger) (double dagger).,Zhang P, Martin PD, Purcarea C, Vaishnav A, Brunzelle JS, Fernando R, Guy-Evans HI, Evans DR, Edwards BF Biochemistry. 2009 Jan 7. PMID:19128030 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Aspartate carbamoyltransferase 3D structures

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