Glutathione S-transferase (GST) is a 211 amino acid protein (26kDa) whose DNA sequence is frequently integrated into expression vectors for production of recombinant proteins. The result of expression from this vector is a GST-tagged fusion protein in which the functional GST protein (26kDa) is fused to the N-terminus of the recombinant protein.
Because GST rapidly folds into a stable and highly soluble protein upon translation, inclusion of the GST tag often promotes greater expression and solubility of recombinant proteins than expression without the tag. In addition, GST-tagged fusion proteins can be purified or detected based on the ability of GST (an enzyme) to bind its substrate, glutathione (GSH).