TRYPANOSOMA-CRUZI CDNA ENCODES A TANDEMLY REPEATED DOMAIN-STRUCTURE CHARACTERISTIC OF SMALL STRESS PROTEINS AND GLUTATHIONE S-TRANSFERASES

The isolation, characterization, and expression of a novel cDNA encoding a Trypanosoma cruzi polypeptide (TcAc2), homologous to various small stress proteins and glutathione S-transferases, are described. The deduced amino-acid sequence revealed two domains sharing 27% identity and an additional 27% similarity to each other suggesting that the molecule may have evolved from a single domain by a process of gene duplication and fusion. The TcAc2 cDNA was subcloned into the pGEX-2T vector for expression in E coli. In vitro translation products of epimastigote mRNA, immunoprecipitated with anti-TXepi serum, showed a major radioactive band of 52 kDa. Immunoprecipitation of [S-35]methionine labelled epimastigote and trypomastigote antigens after pulse chase experiments, using anti-TcAc2 fusion protein antibodies, showed that the protein is released into the culture medium. Moreover, Western blot analysis revealed a single band of 52 kDa with epimastigote, trypomastigote and amastigote antigens. Primary structure homology searches revealed that each TcAc2 domain contained within its N-terminus significant homology to Solanum tuberosum pathogenesis-related protein PR1, soybean heat shock protein 26-A, auxin regulated clone pCNT103 from Nicotiana tabacum and Drosophila melanogaster glutathione S-transferase 27 (GST27). This finding was supported by a comparison of hydrophobicity profiles of TcAc2 and these proteins. Most of them play a central role in protection mechanisms against stress. Based on the homology between TcAc2, glutathione S-transferases (GST) and small stress proteins, it is likely that the TcAc2 gene product may play a crucial role in parasite's adaptation to its microenvironment. These molecules could be considered as members of the GST superfamily, where the T cruzi protein may take a particular place because of its internal gene duplication.