<p>Glutaredoxins [<cite idref="PUB00001738"/>, <cite idref="PUB00000560"/>, <cite idref="PUB00002504"/>], also known as thioltransferases (disulphide reductases, are small proteins of approximately one hundred amino-acid residues which utilise glutathione and NADPH as cofactors. Oxidized glutathione is regenerated by glutathione reductase. Together these components compose the glutathione system [<cite idref="PUB00014033"/>]. </p><p>Glutaredoxin functions as an electron carrier in the glutathione-dependent synthesis of deoxyribonucleotides by the enzyme ribonucleotide reductase. Like thioredoxin, which functions in a similar way, glutaredoxin possesses an active centre disulphide bond [<cite idref="PUB00015562"/>]. It exists in either a reduced or an oxidized form where the two cysteine residues are linked in an intramolecular disulphide bond.</p><p>Glutaredoxin has been sequenced in a variety of species. On the basis of extensive sequence similarity, it has been proposed [<cite idref="PUB00005575"/>] that <taxon tax_id="10245">Vaccinia virus</taxon> protein O2L is most probably a glutaredoxin. Finally, it must be noted that <taxon tax_id="10665">Bacteriophage T4</taxon> thioredoxin seems also to be evolutionary related. In position 5 of the pattern T4 thioredoxin has Val instead of Pro.</p><p> This entry of archaeal proteins contains a C-terminal domain with homology to bacterial and eukaryotic glutaredoxins, including a CPYC motif. There is an N-terminal domain which has even more distant homology to glutaredoxins. The name "glutaredoxin" may be inappropriate in the sense of working in tandem with glutathione and glutathione reductase which may not be present in the archaea. The overall domain structure appears to be related to bacterial alkylhydroperoxide reductases, but the homology may be distant enough that the function of this family is wholly different.</p> Glutaredoxin-like domain