Characterization of a cDNA clone encoding the carboxy-terminal domain of a 90-kilodalton surface antigen of Trypanosoma cruzi metacyclic trypomastigotes

We have cloned and sequenced a cDNA for a metacyclic trypomastigote-specific glycoprotein with a molecular mass of 90 kDa, termed MTS-gp90. By immunoblotting, antibodies to the MTS-gp90 recombinant protein reacted exclusively with a 90-kDa antigen of metacyclic trypomastigotes. The insert of the MTS-gp90 cDNA clone strongly hybridized with a single 3.0-kb mRNA of metacyclic forms, whereas the hybridization signal with epimastigote mRNA was weak and those with RNAs from other developmental stages were negative, indicating that transcription of the MTS-gp90 gene is developmentally regulated. A series of experiments showed that the MTS-gp90 gene is present in multiple copies in the Trypanosoma cruzi genome, arranged in a nontandem manner, and that there are at least 40 copies of the gene per haploid genome. Sequence analysis of recombinant MTS-gp90 revealed 40 to 60% identity at the amino acid level with members of a family of mammalian stage-specific, 85-kDa surface antigens of T. cruzi. However, there are considerable differences in the amino acid compositions outside the homology region.