title: Evolutive and  structural characterization of Nostoc commune iron-superoxide dismutase that  is fit for modification.
abstract: Superoxide  dismutase (SOD) has extensive clinical applications for protecting organisms  from toxic oxidation. In this study, the integrated iron-superoxide dismutase  gene (fe-sod) coding sequence of Nostoc commune stain CHEN was  cloned from genomic DNA and compared to sods from other reported algae.  These analyses of immunology and phylogenetics indicated that this Fe-SOD is  considerably homologous with SODs from lower prokaryotes (Fe-SOD or Mn-SOD) but  not those from higher animals (Cu/Zn-SOD). In addition, the N. commune Fe-SOD  shows 67 to 93% protein sequence identity to 10 other algal Fe-SODs (or  Mn-SODs) and 69 to 93% gene sequence identity. Rare nonsynonymous substitutions  imply that algal SODs are being subjected to strong natural selection.  Interestingly, the N. commune Fe-SOD enzyme molecule has a compact  active center that is highly conserved (38.1% of residues are absolutely  conserved), and 2 loose ends localized outside the molecule and inclined to  mutate (only 11.5% of residues are absolutely conserved). Based on associative  analyses of evolution, structure, and function, this special phenomenon is  attributed to function-dependent evolution through negative natural selection.  Under strong natural selection, although the mutation is random on the gene  level, the exterior region is inclined to mutate on the protein level owing to  more nonsynonymous substitutions in the exterior region, which demonstrates the  theoretical feasibility of modifying Fe-SOD on its ends to overcome its  disadvantages in clinical applications.
authors.affiliation: Institution of Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, P.R. China.
authors.forename: Y
authors.initials: Y
authors.lastname: Ma
authors.forename: M
authors.initials: M
authors.lastname: Lu
authors.forename: J-Y
authors.initials: JY
authors.lastname: Li
authors.forename: Y
authors.initials: Y
authors.lastname: Qin
authors.forename: X-G
authors.initials: XG
authors.lastname: Gong
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D050501:Nostoc commune / Q000201:enzymology*; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics*
chemical_list: D013482:Superoxide Dismutase