Glutathione-S-transferase (GST) is an enzyme which has a high affinity for its substrate glutathione and can be purified using immobilised glutathione coated beads (see figures below)
Since there is such a high affinity by GST for its substrate, no other proteins will bind to the column.
Pure fusion protein can be eluted using free reduced glutathione in solution to compete against the immobilised glutathione.
The purity of the product can then be analysed by SDS-PAGE.
