Structural Modeling of Toxoplasma gondii TGME49_289620 Proteinase

Cysteine proteinases play key roles in host-parasite interactions, including host invasion, parasite differentiation, and intracellular survival. Toxoplasma gondii expresses five cysteine proteases, including one cathepsin L‑like (TgCPL), one cathepsin B‑like (TgCPB) and three cathepsin C‑like (TgCPC1, 2 and 3) proteases. We performed the Structural modeling of catalytic domain of TgCPC1 with server I-TASSER, the template selected for homology modeling was Dipeptidyl peptidase I (Cathepsin C) (PDB code: 1JQP). The C-Score of structural modeling of catalytic domain was -0.5; in the L-domain there are nine ɑ-helices and two β-strands and in the right domain there are four β-strands and two ɑ-helices. Cys-440, His-651 and Asn-676, form the cysteine protease catalytic triad in the active site. Adjacent to active site there is a Tyr441 this residue may be involved in the binding of the N terminus of the peptide substrate. A tyrosine residue (Tyr 578) that binds a chloride ion in the crystal structures of rat and human Cathepsin C is also conserved.