Identification of distant caspase homologues in the genome of Trypanosoma cruzi.

ALVAREZ, V.; KOSEC, G.; AGUERO, F.; SÁNCHEZ, D.; DOLINAR, M.; TURK, B.; TURK, V.; CAZZULO, J.J.

Iguazú, Misiones, Argentina.

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular. SAIB 2004.; 2004

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB).

Metacaspases are putative caspase homologues, based on catalytic domain amino acid sequence, His-Cys catalytic diad conservation and predicted secondary structure. They were first identified by PSI-BLAST and are present in plants, fungi and protozoa. So far, five metacaspase genes have been identified in T. brucei. In T. cruzi, however, we found only sequences with homology to TbMCA3 and TbMCA5. TcMCA3 is present in approximately 16 copies per haploid genome arranged in two head-to-tail tandems, while TcMCA5 is present as a single copy. In the vicinity of TcMCA3 ORFs we detected several retrotransposons which probably caused a great amplification of the TcMCA3 gene in T. cruzi and disruption in gene syntheny in comparison to T. brucei. Western blot experiments using antisera against the insoluble recombinant proteins showed that TcMCA3 and TcMCA5 are present in cell free extracts of different life cycle stages of T. cruzi. Although augmented caspase-like activity has been reported in T. cruzi undergoing apoptosis-like cell death, the nature of the enzyme responsible for these observations is not clear. We are producing now soluble recombinant metacaspases in order to determine whether they could be functional homologues to classical caspases.