title: Molecular Cloning and Biochemical Characterization of the Iron Superoxide Dismutase from the Cyanobacterium Nostoc punctiforme ATCC 29133 and Its Response to Methyl Viologen-Induced Oxidative Stress.
abstract: Superoxide dismutase (SOD) detoxifies cell-toxic superoxide radicals and constitutes an important component of antioxidant machinery in aerobic organisms, including cyanobacteria. The iron-containing SOD (SodB) is one of the most abundant soluble proteins in the cytosol of the nitrogen-fixing cyanobacterium Nostoc punctiforme ATCC 29133, and therefore, we investigated its biochemical properties and response to oxidative stress. The putative SodB-encoding open reading frame Npun_R6491 was cloned and overexpressed in Escherichia coli as a C-terminally hexahistidine-tagged protein. The purified recombinant protein had a SodB specific activity of 2560 ± 48 U/mg protein at pH 7.8 and was highly thermostable. The presence of a characteristic iron absorption peak at 350 nm, and its sensitivity to H2O2 and azide, confirmed that the SodB is an iron-containing SOD. Transcript level of SodB in nitrogen-fixing cultures of N. punctiforme decreased considerably (threefold) after exposure to an oxidative stress-generating herbicide methyl viologen for 4 h. Furthermore, in-gel SOD activity analysis of such cultures grown at increasing concentrations of methyl viologen also showed a loss of SodB activity. These results suggest that SodB is not the primary scavenger of superoxide radicals induced by methyl viologen in N. punctiforme.
authors.affiliation: Department of Biotechnology, Mizoram University, PB No. 190, Aizawl, Mizoram, 796004, India.
authors.forename: Lakshmipyari Devi
authors.initials: LD
authors.lastname: Moirangthem
authors.affiliation: Department of Biotechnology, Mizoram University, PB No. 190, Aizawl, Mizoram, 796004, India.
authors.forename: Kalibulla Syed
authors.initials: KS
authors.lastname: Ibrahim
authors.affiliation: Department of Biotechnology, Mizoram University, PB No. 190, Aizawl, Mizoram, 796004, India.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Vanlalsangi
authors.affiliation: Department of Chemistry- Ångström Laboratory, Science for Life Laboratory, Uppsala University, Box 523, 751 20, Uppsala, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Stensjö
authors.affiliation: Department of Chemistry- Ångström Laboratory, Science for Life Laboratory, Uppsala University, Box 523, 751 20, Uppsala, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Lindblad
authors.affiliation: Department of Biotechnology, Mizoram University, PB No. 190, Aizawl, Mizoram, 796004, India. jyotirmoyb@rediffmail.com.
authors.forename: Jyotirmoy
authors.initials: J
authors.lastname: Bhattacharya
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D019295:Computational Biology; D016166:Free Radical Scavengers / Q000378:metabolism; D006540:Herbicides / Q000633:toxicity; D006863:Hydrogen-Ion Concentration; D046937:Nostoc / Q000201:enzymology* / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects*; D010269:Paraquat / Q000633:toxicity*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D016166:Free Radical Scavengers; D006540:Herbicides; D011994:Recombinant Proteins; C087504:SodB protein, Bacteria; D013482:Superoxide Dismutase; D010269:Paraquat
keywords: Cyanobacteria; Iron superoxide dismutase; Methyl viologen; Nostoc punctiforme; Oxidative stress; SodB overexpression; SodB transcript