Glutaredoxins are proteins known to be a part of certain redox reactions by serving as thiol-disulphide oxidoreductases which use thioredoxin (Trx) fold architecture and a Cxx active site. They are able to bind to labile iron-sulphur clusters and carry them to certain acceptor proteins. Glutaredoxins also seem to have a role in the sensing of iron within the cell, and they are also able to serve as scaffold proteins for the de novo synthesis of iron-sulphur clusters.
Glutaredoxins (Grxs) have been known to serve as glutathione (GSH)-dependent electron donors for ribonucleotide reductase in E.coli. They are also able to perform glutathionylation, a protein regulatory or cysteine defense mechanism wherea glutathione is covalently bound as a disulphide on a cysteine residue. They have also been known to serve as catalysts for deglutathionylation. Grx5P, the glutaredoxin protein found in mitochondrial yeast cells, is known to contribute to the transfer of preassembled Fe-S clusters from a U-type ISC scaffold protein (Isu 1p) to acceptor proteins. Thus, Grx’s are known to participate in the formation of cluster assembly as well as the transfer of these these clusters. Grxs are also known to contribute to the regulation of iron-responsive genes called the iron regulon present in yeast. Stable Fe-S clusters serve as the redox or iron sensor in this case.
Rouhier, Nicolas, Jeremy Couterier, Michael K. Johnson, and Jean-Pierre Jacquot. "Trends Biochem Sci." Trends Biochem Sci. (2010): n. page.