Together for ever…: Cross-linking of proteins by a ditryptophan bond

Cross-linking of proteins by a ditryptophan bond

by Verônica Paviani

Oxidative modifications of proteins are extensively investigated because proteins are major targets of radicals and oxidants under physiological conditions [1]. The amino acid residues most susceptible to oxidation are the sulfur-containing residues cysteine and methionine and the aromatic residues histidine, phenylalanine, tyrosine and tryptophan. The oxidation of cysteine and methionine residues is reversible and protein-cysteine oxidation is emerging as a fundamental cell regulatory mechanism. In contrast, the oxidation of all other protein residues is irreversible, and may result in loss of protein

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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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