title: A cambialistic superoxide dismutase in the thermophilic photosynthetic bacterium Chloroflexus aurantiacus.
abstract: Superoxide dismutase from the thermophilic anoxygenic photosynthetic bacterium Chloroflexus aurantiacus was cloned, purified, and characterized. This protein is in the manganese- and iron-containing family of superoxide dismutases and is able to use both manganese and iron catalytically. This appears to be the only soluble superoxide dismutase in C. aurantiacus. Iron and manganese cofactors were identified by using electron paramagnetic resonance spectroscopy and were quantified by atomic absorption spectroscopy. By metal enrichment of growth media and by performing metal fidelity studies, the enzyme was found to be most efficient with manganese incorporated, yet up to 30% of the activity was retained with iron. Assimilation of iron or manganese ions into superoxide dismutase was also found to be affected by the growth conditions. This enzyme was also found to be remarkably thermostable and was resistant to H2O2 at concentrations up to 80 mM. Reactive oxygen defense mechanisms have not been previously characterized in the organisms belonging to the phylum Chloroflexi. These systems are of interest in C. aurantiacus since this bacterium lives in a hyperoxic environment and is subject to high UV radiation fluxes.
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA.
authors.forename: Vanessa L
authors.initials: VL
authors.lastname: Lancaster
authors.forename: Russell
authors.initials: R
authors.lastname: LoBrutto
authors.forename: Fabiyola M
authors.initials: FM
authors.lastname: Selvaraj
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
mesh_terms: D000595:Amino Acid Sequence; D041861:Chloroflexus / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008969:Molecular Sequence Data; D010788:Photosynthesis; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics
chemical_list: D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase