title: The active site of arsenite oxidase from Alcaligenes faecalis.
abstract: Arsenite oxidase, a member of the DMSO reductase family of molybdenum enzymes, has two molecules of guanosine dinucleotide molybdenum cofactor coordinating the molybdenum at the active site. X-ray absorption spectroscopy indicates that the Mo-S bonds shorten from 2.47 to 2.37 A upon reduction with the physiological substrate. It also indicates the presence of an oxo ligand at 1.70 A in both oxidized and reduced forms of the enzyme, together with a short, 1.83 A, Mo-O bond in the oxidized form that is lost upon reduction. Resonance Raman spectroscopy indicates that the two pterin dithiolene moieties have different aromaticities, with one, the Q-pterin, having a more discrete dithiolate structure while the other, the P-pterin, has considerable pi-delocalization. Our results indicate that the structure of arsenite oxidase is intermediate between that seen in other molybdenum enzymes, in which one ligand to the metal is provided by the polypeptide (serine, cysteine, or selenocysteine), and tungsten enzymes that lack a peptide ligand.
authors.affiliation: Department of Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Conrads
authors.forename: Craig
authors.initials: C
authors.lastname: Hemann
authors.forename: Graham N
authors.initials: GN
authors.lastname: George
authors.forename: Ingrid J
authors.initials: IJ
authors.lastname: Pickering
authors.forename: Roger C
authors.initials: RC
authors.lastname: Prince
authors.forename: Russ
authors.initials: R
authors.lastname: Hille
mesh_terms: D000421:Alcaligenes / Q000201:enzymology*; D001665:Binding Sites; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D013052:Spectrometry, X-Ray Emission; D013059:Spectrum Analysis, Raman
chemical_list: D010088:Oxidoreductases; C078179:arsenite oxidase