title: Hypochlorous acid and myeloperoxidase-catalyzed oxidation of iron-sulfur clusters in bacterial respiratory dehydrogenases.
abstract: Hypochlorous acid and related oxidants derived from myeloperoxidase-catalyzed reactions contribute to the microbicidal activities of phagocytosing neutrophils and monocytes. Microbial iron-sulfur (Fe/S) clusters have been suggested as general targets of myeloperoxidase-derived oxidations, but no susceptible Fe/S site has yet been identified. In this study, the effects of HOCl and myeloperoxidase-catalyzed peroxidation of chloride ion upon EPR-detectable Fe/S clusters in Escherichia coli and Pseudomonas aeruginosa were examined. Increasing amounts of oxidant produced progressive loss of signal amplitudes from the S-1 and S-3 Fe/S clusters of succinate:ubiquinone oxidoreductase in respiring membrane fragments. These changes were compared to loss of microbial viability, succinate uptake rates, succinate dehydrogenase activity and succinate-dependent respiration. The amounts of oxidant required to destroy Fe/S clusters exceeded the amounts required to kill organisms or inhibit respiratory function by factors of four or five. Power saturation characteristics of the S-1 signal indicated that the S-2 signal was also resistant to modification, even in highly oxidized membranes. Loss of succinate-dependent respiration was closely associated with HOCl and myeloperoxidase-mediated microbicidal activity against P. aeruginosa and was also an early event in the oxidant-mediated metabolic dysfunctions of E. coli. However, these effects were not caused by the destruction of the Fe/S clusters within the succinate:ubiquinone oxidoreductase. Rather, the major respiration-inhibiting lesion(s) appeared to reside at points in the respiratory chain between the Fe/S clusters and the ubiquinone reductase site.
authors.affiliation: Department of Chemical and Biological Sciences, Oregon Graduate Institute of Science and Technology, Beaverton 97006-1999.
authors.forename: J K
authors.initials: JK
authors.lastname: Hurst
authors.forename: W C
authors.initials: WC
authors.lastname: Barrette
authors.forename: B R
authors.initials: BR
authors.lastname: Michel
authors.forename: H
authors.initials: H
authors.lastname: Rosen
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D042963:Electron Transport Complex II; D004926:Escherichia coli / Q000201:enzymology*; D006997:Hypochlorous Acid; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D007700:Kinetics; D009097:Multienzyme Complexes / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D013385:Succinate Dehydrogenase / Q000378:metabolism*
chemical_list: D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; D006997:Hypochlorous Acid; D010088:Oxidoreductases; D009195:Peroxidase; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase