Repair of oxidized proteins in Trypanosoma cruzi: Functional characterization of methionine sulfoxide reductase B.

DIEGO G ARIAS; ALBERTO A IGLESIAS; SERGIO A GUERRERO

Mar del Plata

Congreso; Reunión de la SAP; 2014

Methionine is an amino acid susceptible to being oxidized to methionine sulfoxide (MetSO). The reduction of MetSO to methionine is catalyzed by methionine sulfoxide reductase (MSR), an enzyme present in almost all organisms. In trypanosomatids, the study of antioxidant systems has been mainly focused on the involvement of trypanothione, a specific redox component in these organisms. However, poorly information is available concerning their mechanisms for repairing oxidized proteins, which would be relevant for the survival of these pathogens in the various stages of their life cycle. Recently, we characterized two A-type MSR proteins from T. cruzi and T. brucei. In this work, we report the molecular cloning of a gene encoding a putative B‑type MSR in this pathogen. The gene was expressed in Escherichia coli, and the corresponding recombinant protein was purified and functionally characterized. The enzyme was specific for L-Met(R)SO reduction, using T. cruzi TXNI, TXNII and TRX as the reducing substrates. In addition, we found that TcMSRB could compensate for MSR deficiency in yeast mutant strain lacking both MSRA and MSRB genes. The protein presented redox-dependent change in monomer/dimer oligomerization states. The in vivo presence of the enzymes was evidenced by immunological detection in replicative and infective stages of T. cruzi. Overexpression of TcMSRB in epimastigote cells confers resistance to oxidative stress. The results support the occurrence of a metabolic pathway in T.cruzi involved in the critical function of repairing oxidized macromolecules.