Acta Cryst. (2005). D61, 218-229 [doi:10.1107/S0907444904031531]
Abstract: Urate oxidase from Aspergillus flavus (uricase or Uox; EC 1.7.3.3) is a 135 kDa homotetramer with a subunit consisting of 301 amino acids. It catalyses the first step of the degradation of uric acid into allantoin. The structure of the extracted enzyme complexed with a purine-type inhibitor (8-azaxanthin) had been solved from high-resolution X-ray diffraction of I222 crystals. Expression of the recombinant enzyme in Saccharomyces cerevisiae followed by a new purification procedure allowed the crystallization of both unliganded and liganded enzymes utilizing the same conditions but in various crystal forms. Here, four different crystal forms of Uox are analyzed. The diversity of the Uox crystal forms appears to depend strongly on the chemicals used as inhibitors. In the presence of uracil and 5,6-diaminouracil crystals usually belong to the trigonal space group P3121, the asymmetric unit (AU) of which contains one tetramer of Uox (four subunits). Chemical oxidation of 5,6-diaminouracil within the protein may occur, leading to the canonical (I222) packing with one subunit per AU. Coexistence of two crystal forms, P21 with two tetramers per AU and I222, was found in the same crystallization drop containing another inhibitor, guanine. Finally, a fourth form, P21212 with one tetramer per AU, resulted fortuitously in the presence of cymelarsan, an additive. Of all the reported forms, the I222 crystal forms present by far the best X-ray diffraction resolution (
1.6 Å resolution compared with 2.3-3.2 Å for the other forms). The various structures and contacts in all crystalline lattices are compared. The backbones are essentially conserved except for the region near the active site. Its location at the dimer interface is thus likely to be at the origin of the crystal contact changes as a response to the various bound inhibitors.
PDB references: 1ws3, 1ws2, 1wrr, 1xxj, 1xy3 and 1xt4
Keywords: urate oxidase; Aspergillus flavus; inhibition; polymorphism; packing; uracil; 5,6-diaminouracil; guanine.
 |   PDF file (60.4 kbytes) |
To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.
The download button will force most browsers to prompt for a file name to store the data on your hard disk.
Where possible, images are represented by thumbnails.
If the supplementary material that you require is not shown in the list above, it may only be available in our hard-copy archive. However, our policy is to progressively digitize old hard-copy supplementary documents where possible.
Please help us to work towards this goal by completing the form below. This will register your wish to receive a supplementary document, which we shall scan to create a PDF and then make available via the web to you and to other requestors in the future.
Copyright © International Union of Crystallography
IUCr Webmaster