title: Nature of halide binding to the molybdenum site of sulfite oxidase.
abstract: Valuable information on the active sites of molybdenum enzymes has been provided from both Mo(V) electron paramagnetic resonance (EPR) spectroscopy and X-ray absorption spectroscopy (XAS). One of three major categories of Mo(V) EPR signals from the molybdenum enzyme sulfite oxidase is the low-pH signal, which forms in the presence of chloride. Two alternative structures for this species have been proposed, one in which the chloride is coordinated directly to Mo and a second in which chloride is held in the arginine-rich basic pocket some 5 Å from Mo. Here we present an independent assessment of the structure of this species by using XAS of the analogous bromide and iodide complexes. We show that there is no evidence of direct Mo-I coordination, and that the data are consistent with a structure in which the halide is bound at ∼5 Å from Mo.
authors: Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada.
authors: M Jake
authors: MJ
authors: Pushie
authors: Christian J
authors: CJ
authors: Doonan
authors: Heather L
authors: HL
authors: Wilson
authors: K V
authors: KV
authors: Rajagopalan
authors: Graham N
authors: GN
authors: George
mesh_terms: D001665:Binding Sites; D001965:Bromides / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D007454:Iodides / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D008982:Molybdenum / Q000737:chemistry*; D050876:Sulfite Oxidase / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D001965:Bromides; D007454:Iodides; D008982:Molybdenum; D050876:Sulfite Oxidase