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|2w3s, resolution 2.60Å ()|
|Ligands:||, , , , ,|
|Related:|| 1jrp, 1jro, 2w3r
CRYSTAL STRUCTURE OF XANTHINE DEHYDROGENASE (DESULFO FORM) FROM RHODOBACTER CAPSULATUS IN COMPLEX WITH XANTHINE
Rhodobacter capsulatus xanthine dehydrogenase (XDH) is an (alphabeta)(2) heterotetrameric cytoplasmic enzyme that resembles eukaryotic xanthine oxidoreductases in respect to both amino acid sequence and structural fold. To obtain a detailed understanding of the mechanism of substrate and inhibitor binding at the active site, we solved crystal structures of R. capsulatus XDH in the presence of its substrates hypoxanthine, xanthine, and the inhibitor pterin-6-aldehyde using either the inactive desulfo form of the enzyme or an active site mutant (E(B)232Q) to prevent substrate turnover. The hypoxanthine- and xanthine-bound structures reveal the orientation of both substrates at the active site and show the importance of residue Glu(B)-232 for substrate positioning. The oxygen atom at the C-6 position of both substrates is oriented toward Arg(B)-310 in the active site. Thus the substrates bind in an orientation opposite to the one seen in the structure of the reduced enzyme with the inhibitor oxypurinol. The tightness of the substrates in the active site suggests that the intermediate products must exit the binding pocket to allow first the attack of the C-2, followed by oxidation of the C-8 atom to form the final product uric acid. Structural studies of pterin-6-aldehyde, a potent inhibitor of R. capsulatus XDH, contribute further to the understanding of the relative positioning of inhibitors and substrates in the binding pocket. Steady state kinetics reveal a competitive inhibition pattern with a K(i) of 103.57 +/- 18.96 nm for pterin-6-aldehyde.
Mechanism of Substrate and Inhibitor Binding of Rhodobacter capsulatus Xanthine Dehydrogenase., Dietzel U, Kuper J, Doebbler JA, Schulte A, Truglio JJ, Leimkuhler S, Kisker C, J Biol Chem. 2009 Mar 27;284(13):8768-76. Epub 2008 Dec 24. PMID:19109249
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
About this Structure
- Dietzel U, Kuper J, Doebbler JA, Schulte A, Truglio JJ, Leimkuhler S, Kisker C. Mechanism of Substrate and Inhibitor Binding of Rhodobacter capsulatus Xanthine Dehydrogenase. J Biol Chem. 2009 Mar 27;284(13):8768-76. Epub 2008 Dec 24. PMID:19109249 doi:10.1074/jbc.M808114200
- Steere AN, Byrne SL, Chasteen ND, Smith VC, Macgillivray RT, Mason AB. Evidence that His349 acts as a pH-inducible switch to accelerate receptor-mediated iron release from the C-lobe of human transferrin. J Biol Inorg Chem. 2010 Aug 14. PMID:20711621 doi:10.1007/s00775-010-0694-2 20711621 10.1007/s00775-010-0694-2