2e25

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spinqualitylabelsall models 2e25, resolution 2.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

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

Overview

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.

About this Structure

2E25 is a Single protein structure of sequence from Escherichia coli with and as ligands. Active as Dihydroorotase, with EC number 3.5.2.3 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 Crystallograph Sect F Struct Biol Cryst Commun. 2007 Mar 1;63(Pt, 3):154-61. Epub 2007 Feb 13. PMID:17329804

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