The rise of H2O2 concentration that characterizes the initiation of apoptosis can specifically oxidize Met80 in cytochrome c bound to zwitterionic phospholipids, yielding a stable peroxidase.
Trypanosoma cruzi tryparedoxin 1 (TcTXN1) is an oxidoreductase belonging to the thioredoxin superfamily, which mediates electron transfer between trypanothione and peroxiredoxins. In trypanosomes TXNs, and not thioredoxins, constitute the oxido-reductases of peroxiredoxins. Since, to date, there is no information concerning TcTXN1 substrates in T. cruzi, the aim of this work was to characterize TcTXN1 in two aspects: expression throughout T. cruzi life cycle and subcellular localization; and the study of TcTXN1 interacting-proteins. We demonstrate that TcTXN1 is a cytosolic and constitutively expressed protein in T. cruzi. In order to start to unravel the redox interactome of T. cruzi we designed an active site mutant protein lacking the resolving cysteine, and validated the complex formation in vitro between the mutated TcTXN1 and a known partner, the cytosolic peroxiredoxin. Through the expression of this mutant protein in parasites with an additional 6xHis-tag, heterodisulfide complexes were isolated by affinity chromatography and identified by 2-DE/MS. This allowed us to identify fifteen TcTXN1 proteins which are involved in two main processes: oxidative metabolism and protein synthesis and degradation. Our approach led us to the discovery of several putatively TcTXN1-interacting proteins thereby contributing to our understanding of the redox interactome of T. cruzi.
The cestodes constitute important but understudied human and veterinary parasites. Their surfaces are rich in carbohydrates, on which very little structural information is available. The tissue-dwelling larva (hydatid cyst) of the cestode Echinococcus granulosus is outwardly protected by a massive layer of carbohydrate-rich extracellular matrix, termed the laminated layer. The monosaccharide composition of this layer suggests that its major carbohydrate components are exclusively mucin-type O-glycans. We have purified these glycans after their release from the crude laminated layer and obtained by MS and NMR the complete structure of 10 of the most abundant components. The structures, between two and six residues in length, encompass a limited number of biosynthetic motifs. The mucin cores 1 and 2 are either nondecorated or elongated by a chain of Galpbeta1-3 residues. This chain can be capped by a single Galpalpha1-4 residue, such capping becoming more dominant with increasing chain size. In addition, the core 2 N-acetylglucosamine residue is in cases substituted with the disaccharide Galpalpha1-4Galpbeta1-4, giving rise to the blood P(1)-antigen motif. Larger, also related, glycans exist, reaching at least 18 residues in size. The glycans described are related but larger than those previously described from an Echinococcus multilocularis mucin [Hulsmeier, A. J., et al. (2002) J. Biol. Chem. 277, 5742-5748]. Our results reveal that the E. granulosus cyst exposes to the host only a few different major carbohydrate motifs. These motifs are composed essentially of galactose units and include the elongation by (Galpbeta1-3)(n) and the capping by Galpalpha1-4, novel in animal mucin-type O-glycans.
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