title: Superoxidized states of Escherichia coli sulfite reductase heme protein subunit.
abstract: The oxidized forms of resting and sulfite-complexed Escherichia coli sulfite reductase heme protein subunit react with near-stoichiometric amounts of porphyrexide to produce what is best characterized as a ferrisiroheme pi cation radical. Addition of either sodium ascorbate or NADPH completely regenerates the parent form. Implications of these findings with respect to mechanisms of metal-radical J coupling and catalysis are discussed.
authors.affiliation: Department of Biochemistry, Duke University, Durham, North Carolina 27705.
authors.forename: L J
authors.initials: LJ
authors.lastname: Young
authors.forename: L M
authors.initials: LM
authors.lastname: Siegel
mesh_terms: D004926:Escherichia coli / Q000201:enzymology*; D005609:Free Radicals; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000378:metabolism*; D011166:Porphyrins; D011487:Protein Conformation; D013053:Spectrophotometry; D050864:Sulfite Reductase (NADPH)
chemical_list: D005609:Free Radicals; D011166:Porphyrins; C031553:porphyrexide; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors; D050864:Sulfite Reductase (NADPH); C494314:sulfite reductase (NADPH), E coli