Molecular cloning and characterization of two iron superoxide dismutase cDNAs from Trypanosoma cruzi

Two cDNAs (FeSODA and FeSODB cDNAs) corresponding to superoxide dismutase (1.15.1.1., SOD) were isolated from a Trypanosoma cruzi cDNA library. Comparison of the deduced amino acid sequences with previously reported SOD protein sequences revealed that the T. cruzi open reading frames had considerable homology with FeSODs. The coding region of the T. cruzi FeSODB cDNA has been expressed in fusion with glutathione-S-transferase using an Escherichia coli mutant QC779, lacking both MnSOD and FeSOD genes (sodA sodB). Staining of native polyacrylamide gels for SOD activity of T cruzi crude lysate and the recombinant SOD suggests that this protein is an FeSOD. The recombinant enzyme also protected the E. coli mutant QC779 from paraquat toxicity. Northern blot analysis showed that FeSODB is differentially expressed, showing a higher level at the epimastigote stage of T. cruzi development; whereas, FeSODA is constitutively expressed at a lower level in all developmental stages. Furthermore, Southern hybridization shows that both FeSODA and FeSODB genes appear to be present in the T. cruzi genome as multiple repeating units (multi-copy gene family).