Schistosoma mansoni: identification and analysis of an mRNA and a gene encoding superoxide dismutase (Cu/Zn)

The sequence of an mRNA encoding superoxide dismutase (EC 1.15.1.1) of Schistosoma mansoni has been determined. The deduced amino acid sequence which it encodes shows 40 to 45% homology with the amino acid sequences of the cytosolic superoxide dismutase from 10 other species, as well as similar homology with the human extracellular form. Hybridization selection of the mRNA by cDNA clone pSM38 and in vitro translation of this mRNA have consistently produced a protein of 20,000 Da and occasionally, a 40,000-Da protein. Both are immunoprecipitable with sera pooled from patients with chronic schistosomiasis. The gene from which this mRNA is transcribed has also been isolated and characterized. It spans 5.1 kb of chromosomal DNA and possesses three exons and two introns which interrupt the coding region. These introns contain the splice junction sequences which fit the consensus sequences observed in mammalian genes. The upstream sequence of the gene shows a region for a potential 'TATA' box and the downstream sequence contains two polyadenylation sites.