Trypanosoma cruzi cDNA encodes a tandemly repeated domain structure characteristic of small stress proteins and glutathione S‐transferases

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Abstract
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 [35S] 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 PRI, 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.

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