1j79: Difference between revisions
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[[Image:1j79.gif|left|200px]] | [[Image:1j79.gif|left|200px]] | ||
'''Molecular Structure of Dihydroorotase: A Paradigm for Catalysis Through the Use of a Binuclear Metal Center''' | {{Structure | ||
|PDB= 1j79 |SIZE=350|CAPTION= <scene name='initialview01'>1j79</scene>, resolution 1.70Å | |||
|SITE= | |||
|LIGAND= <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene>, <scene name='pdbligand=ORO:OROTIC+ACID'>ORO</scene> and <scene name='pdbligand=NCD:N-CARBAMOYL-L-ASPARTATE'>NCD</scene> | |||
|ACTIVITY= [http://en.wikipedia.org/wiki/Dihydroorotase Dihydroorotase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.2.3 3.5.2.3] | |||
|GENE= PYRC ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=562 Escherichia coli]) | |||
}} | |||
'''Molecular Structure of Dihydroorotase: A Paradigm for Catalysis Through the Use of a Binuclear Metal Center''' | |||
==Overview== | ==Overview== | ||
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==About this Structure== | ==About this Structure== | ||
1J79 is a [ | 1J79 is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1J79 OCA]. | ||
==Reference== | ==Reference== | ||
Molecular structure of dihydroorotase: a paradigm for catalysis through the use of a binuclear metal center., Thoden JB, Phillips GN Jr, Neal TM, Raushel FM, Holden HM, Biochemistry. 2001 Jun 19;40(24):6989-97. PMID:[http:// | Molecular structure of dihydroorotase: a paradigm for catalysis through the use of a binuclear metal center., Thoden JB, Phillips GN Jr, Neal TM, Raushel FM, Holden HM, Biochemistry. 2001 Jun 19;40(24):6989-97. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/11401542 11401542] | ||
[[Category: Dihydroorotase]] | [[Category: Dihydroorotase]] | ||
[[Category: Escherichia coli]] | [[Category: Escherichia coli]] | ||
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[[Category: tim barrel]] | [[Category: tim barrel]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Mar 20 11:59:33 2008'' | ||
Revision as of 12:59, 20 March 2008
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| , resolution 1.70Å | |||||||
|---|---|---|---|---|---|---|---|
| Ligands: | , and | ||||||
| Gene: | PYRC (Escherichia coli) | ||||||
| Activity: | Dihydroorotase, with EC number 3.5.2.3 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Molecular Structure of Dihydroorotase: A Paradigm for Catalysis Through the Use of a Binuclear Metal Center
OverviewOverview
Dihydroorotase plays a key role in pyrimidine biosynthesis by catalyzing the reversible interconversion of carbamoyl aspartate to dihydroorotate. Here we describe the three-dimensional structure of dihydroorotase from Escherichia coli determined and refined to 1.7 A resolution. Each subunit of the homodimeric enzyme folds into a "TIM" barrel motif with eight strands of parallel beta-sheet flanked on the outer surface by alpha-helices. Unexpectedly, each subunit contains a binuclear zinc center with the metal ions separated by approximately 3.6 A. Lys 102, which is carboxylated, serves as a bridging ligand between the two cations. The more buried or alpha-metal ion in subunit I is surrounded by His 16, His 18, Lys 102, Asp 250, and a solvent molecule (most likely a hydroxide ion) in a trigonal bipyramidal arrangement. The beta-metal ion, which is closer to the solvent, is tetrahedrally ligated by Lys 102, His 139, His 177, and the bridging hydroxide. L-Dihydroorotate is observed bound to subunit I, with its carbonyl oxygen, O4, lying 2.9 A from the beta-metal ion. Important interactions for positioning dihydroorotate into the active site include a salt bridge with the guanidinium group of Arg 20 and various additional electrostatic interactions with both protein backbone and side chain atoms. Strikingly, in subunit II, carbamoyl L-aspartate is observed binding near the binuclear metal center with its carboxylate side chain ligating the two metals and thus displacing the bridging hydroxide ion. From the three-dimensional structures of the enzyme-bound substrate and product, it has been possible to propose a unique catalytic mechanism for dihydroorotase. In the direction of dihydroorotate hydrolysis, the bridging hydroxide attacks the re-face of dihydroorotate with general base assistance by Asp 250. The carbonyl group is polarized for nucleophilic attack by the bridging hydroxide through a direct interaction with the beta-metal ion. During the cyclization of carbamoyl aspartate, Asp 250 initiates the reaction by abstracting a proton from N3 of the substrate. The side chain carboxylate of carbamoyl aspartate is polarized through a direct electrostatic interaction with the binuclear metal center. The ensuing tetrahedral intermediate collapses with C-O bond cleavage and expulsion of the hydroxide which then bridges the binuclear metal center.
About this StructureAbout this Structure
1J79 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
Molecular structure of dihydroorotase: a paradigm for catalysis through the use of a binuclear metal center., Thoden JB, Phillips GN Jr, Neal TM, Raushel FM, Holden HM, Biochemistry. 2001 Jun 19;40(24):6989-97. PMID:11401542
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