title: Multifrequency cw-EPR investigation of the catalytic molybdenum cofactor of polysulfide reductase from Wolinella succinogenes.
abstract: Electron paramagnetic resonance (EPR) spectra of the molybdenum centre in polysulfide reductase (Psr) from Wolinella succinogenes with unusually high G-tensor values have been observed for the first time. Three different Mo(V) states have been generated (by the addition of the substrate polysulfide and different redox agents) and analysed by their G- and hyperfine tensors using multifrequency (S-, X- and Q-band) cw-EPR spectroscopy. The unusually high G-tensor values are attributed to a large number of sulfur ligands. Four sulfur ligands are assumed to arise from two pterin cofactors; one additional sulfur ligand was identified from mutagenesis studies to be a cysteine residue of the protein backbone. One further sulfur ligand is proposed for two of the Mo(V) states, based on the experimentally observed shift of the g(av) value. This sixth sulfur ligand is postulated to belong to the polysulfide substrate consumed within the catalytic reaction cycle of the enzyme. The influence of the co-protein sulfur transferase on the Mo(V) G-tensor supports this assignment.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe-University Frankfurt, Marie-Curie-Strasse 11, 60439, Frankfurt am Main, Germany. prisner@chemie.uni-frankfurt.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Prisner
authors.forename: Sevdalina
authors.initials: S
authors.lastname: Lyubenova
authors.forename: Yener
authors.initials: Y
authors.lastname: Atabay
authors.forename: Fraser
authors.initials: F
authors.lastname: MacMillan
authors.forename: Achim
authors.initials: A
authors.lastname: Kröger
authors.forename: Oliver
authors.initials: O
authors.lastname: Klimmek
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis* / Q000378:metabolism; D002384:Catalysis; D003067:Coenzymes / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D008667:Metalloproteins / Q000032:analysis*; D008982:Molybdenum / Q000378:metabolism*; D000090006:Molybdenum Cofactors; D010088:Oxidoreductases / Q000032:analysis* / Q000378:metabolism; D011621:Pteridines / Q000032:analysis*; D016968:Wolinella / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D003067:Coenzymes; D008667:Metalloproteins; D008982:Molybdenum; D000090006:Molybdenum Cofactors; D010088:Oxidoreductases; D011621:Pteridines; C022261:molybdopterin; C074883:polysulfide reductase