Molecular characterization of a 2-Cys peroxiredoxin from the human malariaparasite Plasmodium falciparum

We have identified the 2-Cys peroxiredoxin (PfPrx-1) from the human malaria parasite Plasmodium falciparum. The PfPrx-1 showed the highest identity at amino acid level to the type Il Prx among the currently known six subfamil ies of mammalian Prx. The sequence identity between the PfPrx-1 and the pre viously reported I-Cys Prx. of P. falciparum (PfPrx-2), which corresponded to mammalian type VI Prx, was 25%. This suggests that the parasite possesse s two Prx subfamilies. The PfPrx-1 showed significant sequence similarities with those of 2-Cys peroxiredoxins of plants in the BLASTX search. This ma y reflect the consequences of a genetic transfer from an algal endosymbiont to the parasite nucleus during evolution. The recombinant PfPrx-1 protein (rPfPrx-1) was expressed as a histidine fusion protein in Escherichia coli and purified with Ni chromatography. The rPfPrx-1 existed as dimers under n on-reducing conditions and dissociated into monomers in the presence of dit hiothreitol. The PfPrx-1 protein also exists as a dimer in the parasites th emselves. The reduction of the oxidized enzyme by the donation of electrons from E. coli thioredoxin (Trx)/Trx reductase system was demonstrated in it s reaction with H2O2, using the rPfPrx-1 protein. These results suggested t hat the PfPrx-1 can act as a terminal peroxidase of the parasite Trx system . An elevated expression of the PfPrx-1 protein seen in the trophozoite, th e stage with active metabolism, suggests an association of the parasite Trx . system with its intracellular redox control. (C) 2001 Elsevier Science B. V. All rights reserved.