This post was contributed by guest blogger Jon Backstrom, a biochemist in the Vanderbilt Eye Institute and Tonia Rex's lab.
A common strategy to determine the binding kinetics of a purified protein involves immobilization on a solid support. This allows washing away of unbound material to calculate the amount of bound ligand (after subtracting out non-specific binding). Historically, glutathione-S-transferase (GST) fusion proteins have been immobilized on a reduced glutathione matrix. The advantage of a fusion protein is the efficient purification of an already immobilized target protein. The disadvantage is that the GST moiety, which forms dimers, may influence binding kinetics of the target ligand. Another important consideration is whether the affinity of an experimental protein-ligand interaction approaches that of GST-glutathione.