3D6N

Crystal Structure of Aquifex Dihydroorotase Activated by Aspartate Transcarbamoylase

3D6N の概要

• エントリーDOI: 10.2210/pdb3d6n/pdb
• 関連するPDBエントリー: 1xrf 1xrt
• 分子名称: Dihydroorotase, Aspartate carbamoyltransferase, ZINC ION, ... (5 entities in total)
• 機能のキーワード: reactor, chamber, pores, internal cavity, hydrolase, metal-binding, pyrimidine biosynthesis, transferase, hydrolase-transferase complex, hydrolase/transferase
• 由来する生物種: Aquifex aeolicus; 詳細
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 80490.88

構造登録者

Edwards, B.F.P. (登録日: 2008-05-20, 公開日: 2009-01-20, 最終更新日: 2023-08-30)

主引用文献

Zhang, P.,Martin, P.D.,Purcarea, C.,Vaishnav, A.,Brunzelle, J.S.,Fernando, R.,Guy-Evans, H.I.,Evans, D.R.,Edwards, B.F.
Dihydroorotase from the hyperthermophile Aquifiex aeolicus is activated by stoichiometric association with aspartate transcarbamoylase and forms a one-pot reactor for pyrimidine biosynthesis.
Biochemistry, 48:766-778, 2009

PubMed Abstract: 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.

PubMed: 19128030
DOI: 10.1021/bi801831r

実験手法

X-RAY DIFFRACTION (2.3 Å)