2e25

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{{STRUCTURE_2e25| PDB=2e25 | SCENE= }}
{{STRUCTURE_2e25| PDB=2e25 | SCENE= }}
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'''The Crystal Structure of the T109S mutant of E. coli Dihydroorotase complexed with an inhibitor 5-fluoroorotate'''
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===The Crystal Structure of the T109S mutant of E. coli Dihydroorotase complexed with an inhibitor 5-fluoroorotate===
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==Overview==
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Crystals of a single-point mutant (T109S) of Escherichia coli dihydroorotase (DHOase) with diminished activity grown in the presence of L-dihydroorotate (L-DHO) are tetragonal, with a monomer in the asymmetric unit. These crystals are extremely unstable and disintegrate shortly after formation, which is followed by the growth of orthorhombic crystals from the remnants of the tetragonal crystals or at new nucleation sites. Orthorhombic crystals, for which a structure has previously been reported [Thoden et al. (2001), Biochemistry, 40, 6989-6997; Lee et al. (2005), J. Mol. Biol. 348, 523-533], contain a dimer of DHOase in the asymmetric unit; the active site of one monomer contains the substrate N-carbamyl-L-aspartate (L-CA-asp) and the active site of the other monomer contains the product of the reaction, L-DHO. In the subunit with L-DHO in the active site, a surface loop (residues 105-115) is 'open'. In the other subunit, with L-CA-asp in the active site, the loop folds inwards, forming specific hydrogen bonds from the loop to the L-CA-asp. The tetragonal crystal form can be stabilized by crystallization in the presence of the inhibitor 5-fluoroorotate (FOA), a product (L-DHO) mimic. Crystals of the complex of T109S DHOase with FOA are tetragonal, space group P4(1)2(1)2, with unit-cell parameters a = b = 72.6, c = 176.1 A. The structure has been refined to R and R(free) values of 0.218 and 0.257, despite severe anisotropy of the diffraction. In this structure, the flexible loops are both in the 'open' conformation, which is consistent with FOA, like L-DHO, binding at both sites. The behaviour of the T109S mutant crystals of DHOase in the presence of L-DHO is explained by initial binding of L-DHO to both subunits, followed by slow conversion to L-CA-asp, with consequent movement of the flexible loop and dissolution of the crystals. Orthorhombic crystals are then able to grow in the presence of L-DHO and L-CA-asp.
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(as it appears on PubMed at http://www.pubmed.gov), where 17329804 is the PubMed ID number.
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{{ABSTRACT_PUBMED_17329804}}
==About this Structure==
==About this Structure==
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[[Category: Maher, M J.]]
[[Category: Maher, M J.]]
[[Category: Tim barrel]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 11:25:20 2008''

Revision as of 08:25, 29 July 2008

Template:STRUCTURE 2e25

The Crystal Structure of the T109S mutant of E. coli Dihydroorotase complexed with an inhibitor 5-fluoroorotate

Template:ABSTRACT PUBMED 17329804

About this Structure

2E25 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Structure of the T109S mutant of Escherichia coli dihydroorotase complexed with the inhibitor 5-fluoroorotate: catalytic activity is reflected by the crystal form., Lee M, Maher MJ, Guss JM, Acta Crystallogr Sect F Struct Biol Cryst Commun. 2007 Mar 1;63(Pt, 3):154-61. Epub 2007 Feb 13. PMID:17329804

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