Epitope tagging offers an easy and universal strategy for the identification and purification of proteins derived by recombinant DNA technology. Expression vectors with Glutathione S-transferase (GST) tag have beed developed widely for both prokaryotic and eukaryotic systems, because GST can provides both an easily detectable Tag and a simple purification process with little effect on the biological function of the protein encoded by inserted cDNA sequences. Antibodies of anti-GST tag are useful for checking protein expression using immunoblotting, immunoprecipitation and immunostaining techniques, as well as for immunoaffinity purification of protein expressed in vitro.