Metacaspases-Like Proteases of Trichomonas vaginalis: In Silico Identification and Characterization.

Metacaspases (MCA), are cysteine-dependent proteases closely related to caspases. In protozoa, MCA plays an important role in programmed cell death (PCD). In Trichomonas vaginalis, a kind of PCD that resembles apoptosis has been described, but the activators of this mechanism have not been demonstrated. We performed a genome-wide in silico analysis in the T. vaginalis database using consensus MCA domains. A total of 15 protein annotations for MCA-like sequences were retrieved. Only 7/15 (TvMCA1-6 and TvMCA9) of the sequences were annotated as putative MCA and exhibited a similar range of amino acid length in comparison to the consensus sequences used for the query. By in silico analysis, we found that they are thermostable, hydrophilic proteins with molecular weights ranging from 27 to 33 KDa and their theoretical isoelectric points are in a 5.08-8.57 range. The phylogenetic analysis showed the similarity of conserved motifs for the predicted TvMCA proteins. 3D structure prediction by homology modeling demonstrated that TvMCA proteins show a similar conformation to crystallized MCA proteins. Taken together, our results indicate that these trichomonad proteins have conserved sequences like MCA proteins and suggest that they may be responsible for proteolytic activity during a PCD-like mechanism in this parasite.