The two faces of peroxiredoxins

https://commons.wikimedia.org/wiki/File:Janus_coin.png

by Larissa Anastácio da Costa Carvalho

In the antiquity, many cities protected their territories by surrounding fortifications, with giant gates and arches working as unique gateways. The Roman god Janus, known as the protector of entrances or new-beginnings, is represented by a head with two faces in opposite directions. The two faces of Janus symbolize the duality of nature. Well, nature itself is marked by dichotomy. What in nature cannot be good and bad at the same time? That is the origin of the term Janus effect.

A remarkable example of the Janus effect is the mustard gas (1,1-thiobis-2-chloroethane). Used as a chemical weapon during World War I, it causes serious inflammation of the

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Yes, together we can…. A highly conserved histidine residue in 2-Cys peroxiredoxins acts as a pH sensor for oligomerization

by Luis E. S. Netto

Peroxiredoxin (Prx) enzymes are becoming more and more popular among other reasons due to their high reactivity towards hydroperoxides and to their abundance. As a consequence, Prxs are proposed as biological sensors of hydrogen peroxide. It is interesting to observe that since their beginnings (in the end of the 60’s), one feature that called attention was their ability to form high molecular weight species, visible by electron microscopy [1]. It was almost twenty years later that the thiol-dependent peroxidase activity of Prx enzymes was described.

Among Prx family of proteins, 2-Cys Prx enzymes (those belonging to the AhpC/Prx1 group) can adopt a wide array of quartenary

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A comprehensive approach to identify redox and non-redox targets of Trx-like proteins

by Lia S. Nakao

Like the old dictum that says “birds of a feather flock together”, understanding the specific partners of a given protein provides an important clue about its function. Thioredoxin 1 (Trx1) is a well-known redox protein that contains a CXXC motif (cysteines residues flanking two aminoacid residues), responsible for its disulfide reductase function. The first (C-terminal) Cys of the motif attacks the disulfide of the target protein, producing a short lived mixed disulfide, which is reduced by the second (N-terminal resolving) Cys, releasing Trx1 and the target, in the oxidized and reduced forms, respectively. If the resolving Cys is replaced by a non-redox residue, such as

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Peroxide signaling through thiol switches: chemical and biological aspects.

by Luis E. S. Netto

It is now well accepted that oxidants and other redox intermediates are not only damaging compounds, but also act as signaling molecules. This is especially evident for hydrogen peroxide, whose generation and degradation are finely regulated through multiple enzymatic systems. Proteins whose activities are based on Cysteine (Cys) residues are frequently reported to be oxidized in various biological systems in conditions where hydrogen peroxide is also generated. As the most parsimonious hypothesis, these proteins are frequently assumed to be directly oxidized by hydrogen peroxide, although this is not always supported by chemical data.

For instance, Protein Tyrosine Phosphatases

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