<p>In eukaryotes, glutathione S-transferases (GSTs) participate in thedetoxification of reactive electrophillic compounds by catalysing theirconjugation to glutathione. The GST domain is also found in S-crystallins from squid, and proteins with no known GST activity, such as eukaryotic elongation factors 1-gamma and the HSP26 family of stress-related proteins, which include auxin-regulated proteins in plants and stringent starvation proteins in <taxon tax_id="562">Escherichia coli</taxon>. The major lens polypeptide of Cephalopoda is also a GST [<cite idref="PUB00007306"/>, <cite idref="PUB00007307"/>, <cite idref="PUB00007308"/>, <cite idref="PUB00007309"/>].</p><p>Bacterial GSTs of known function often have a specific, growth-supporting role in biodegradative metabolism: epoxide ring opening and tetrachlorohydroquinone reductive dehalogenation are two examples of the reactions catalysed by these bacterial GSTs. Some regulatory proteins, like the stringent starvation proteins, also belong to the GST family [<cite idref="PUB00007310"/>, <cite idref="PUB00007311"/>]. GST seems to be absent from Archaea in which gamma-glutamylcysteine substitute to glutathione as major thiol.</p><p>Soluble GSTs activate glutathione (GSH) to GS-. In many GSTs, this is accomplished by a Tyr at H-bonding distance from the sulphur of GSH. These enzymes catalyse nucleophilic attack by reduced glutathione (GSH) on nonpolar compounds that contain an electrophillic carbon, nitrogen, or sulphur atom [<cite idref="PUB00043691"/>].</p><p>Glutathione S-transferases form homodimers, but in eukaryotes can also form heterodimers of the A1 and A2 or YC1 and YC2 subunits. The homodimeric enzymes display a conserved structural fold, with each monomer composed of two distinct domains [<cite idref="PUB00021969"/>]. The N-terminal domain forms a thioredoxin-like fold that binds the glutathione moiety, while the C-terminal domain contains several hydrophobic alpha-helices that specifically bind hydrophobic substrates.</p><p>This entry represents the C-terminal domain of glutathione S-transferases, and a number of redox-regulated chloride ion channel proteins [<cite idref="PUB00039284"/>].</p>