CRYSTAL-STRUCTURE OF THE XANTHINE OXIDASE-RELATED ALDEHYDE OXIDOREDUCTASE FROM D-GIGAS

The crystal structure of the aldehyde oxido-reductase (Mop) from the s ulfate reducing anaerobic Gram-negative bacterium Desulfovibrio gigas has been determined at 2.25 Angstrom resolution by multiple isomorphou s replacement and refined. The protein, a homodimer of 907 amino acid residues subunits, is a member of the xanthine oxidase family. The pro tein contains a molybdopterin cofactor (Mo-co) and two different [2Fe- 2S] centers. It is folded into four domains of which the first two bin d the iron sulfur centers and the last two are involved in Mo-co bindi ng, Mo-co is a molybdenum molybdopterin cytosine dinucleotide. Molybdo pterin forms a tricyclic system with the pterin bicycle annealed to a pyran ring. The molybdopterin dinucleotide is deeply buried in the pro tein, The cis-dithiolene group of the pyran ring binds the molybdenum, which is coordinated by three more (oxygen) ligands.