Epitope tags are useful for the labeling and detection of proteins using immunoblotting, immunoprecipitation, and immunostaining techniques. Due to their small size, they are unlikely to affect the tagged protein's biochemical properties.
Glutathione S-transferase (GST) is a widely used fusion partner, since it provides both an easily detectable Tag and a simple purification process with little effect on the biological function of the protein of interest. Numerous vectors containing GST-Tag have been developed for both prokaryotic and eukaryotic systems over the past decade.