title: Detection, distribution and characterization of novel superoxide dismutases from Yersinia enterocolitica Biovar 1A.
abstract: BACKGROUND
  Superoxide dismutases (SODs) cause dismutation of superoxide radicals to hydrogen peroxide and oxygen. Besides protecting the cells against oxidative damage by endogenously generated oxygen radicals, SODs play an important role in intraphagocytic survival of pathogenic bacteria. The complete genome sequences of Yersinia enterocolitica strains show presence of three different sod genes. However, not much is known about the types of SODs present in Y. enterocolitica, their characteristics and role in virulence and intraphagocytic survival of this organism.
  
  
  RESULTS
  This study reports detection and distribution of the three superoxide dismutase (sodA, sodB and sodC) genes in 59 strains of Y. enterocolitica and related species. The majority (94%) of the strains carried all three genes and constitutive expression of sodA and sodB was detected in 88% of the strains. Expression of sodC was not observed in any of the strains. The sodA, sodB and sodC genes of Y. enterocolitica were cloned in pET28a (+) vector. Recombinant SodA (82 kDa) and SodB (21 kDa) were expressed as homotetramer and monomer respectively, and showed activity over a broad range of pH (3.0-8.0) and temperature (4-70°C). SodA and SodB showed optimal activity at 4°C under acidic pH of 6.0 and 4.0 respectively. The secondary structures of recombinant SodA and SodB were studied using circular dichroism. Production of YeSodC was not observed even after cloning and expression in E. coli BL21(DE3) cells. A SodA(-) SodB(-) Escherichia coli strain which was unable to grow in medium supplemented with paraquat showed normal growth after complementation with Y. enterocolitica SodA or SodB.
  
  
  CONCLUSIONS
  This is the first report on the distribution and characterization of superoxide dismutases from Y. enterocolitica. The low pH optima of both SodA and SodB encoded by Y. enterocolitica seem to implicate their role in acidic environments such as the intraphagocytic vesicles.
authors.affiliation: Microbial Pathogenicity Laboratory, Department of Microbiology, University of Delhi South Campus, New Delhi, India.
authors.forename: Mahesh Shanker
authors.initials: MS
authors.lastname: Dhar
authors.forename: Vatika
authors.initials: V
authors.lastname: Gupta
authors.forename: Jugsharan Singh
authors.initials: JS
authors.lastname: Virdi
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002942:Circular Dichroism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007526:Isoelectric Point; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018384:Oxidative Stress / Q000235:genetics; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D015008:Yersinia enterocolitica / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D013482:Superoxide Dismutase