Structural studies of the tryparedoxin peroxidase from the human parasite Trypanosoma cruzi.
Piñeyro M.D.1, Pizarro, J.C.2, Lema, F.2, Cayota, A.3, Pritsch O.1, Bentley, G.A.2, Robello C1.
1 Departamento de Bioquímica y 3Departamento Básico de Medicina, Facultad de Medicina, Universidad de la República, Uruguay
2 Unite´ d Immunologie Structurale (CNRS URA 2185), Institut Pasteur.
Trypanosomatids have a unique antioxidant defense againts hydroperoxides, characterized in different parasites of the genera Crithidia, Trypanosoma and Leishmania The tryparedoxin peroxidase (TcTXNPx) catalyzes the reduction of H2O2 or small-chain organic hydroperoxides to alcohols, using tryparedoxin as electron donor, trypanothione, trypanothione reductase and NADPH. The tryparedoxin peroxidase from Trypanosoma cruzi (TcTXNPx) belongs to the family of 2 Cys peroxiredoxins, enzymes with an antioxidant function by means of its peroxidase activity. It has been shown that these enzymes can undergo a redox dependent oligomerization, with a transition between a dimeric and decameric forms in the oxidized and reduced state, respectively.
The aim of this work was the characterization of the enzyme tryparedoxin peroxidase from the human parasite Trypanosoma cruzi.
Methodology and Results: In order to perform structural studies TccTXNPx was, expressed and purified. The structure was solved, and the redox dependent oligomerization of TccTXNPx was studied by gel filtration and electron microscopy in two diferent conditions: oxidation and reduction. In this work we report the first structure of a 2-Cys Prx on its reduced, active form, from a human parasite. The TccTXNPx structure is a ring composed of five dimers. We have analyzed this structure in comparison with other structures of typical 2 Cys peroxiredoxins in both redox states, and derived a list of key residues to explain the structural rearrangement that takes place during the enzymatic cycle. The studies of the redox dependent oligomerization of TccTXNPx had demostrated that this protein do not undergo a decamer to dimer transition as does other Prx.
Conclusions: This knowledge could be of great interest to get further understanding in the peroxide metabolism in these parasites, and it could open the posibility of the design of new specific drugs against trypanosomatids.
This work was supported in part by a C.Robello PDT/DINACYT grant.
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