Epitope Tag Antibody Sampler Kit

Background

Epitope tags are useful for the labeling and detection of proteins using immunoblotting, immunoprecipitation, and immunostaining techniques. Because of their small size, they are unlikely to affect the tagged protein’s biochemical properties.

Several different epitope tags are now commonly utilized and readily available. For instance, a variety of plasmids contain DNA that encodes an amino-terminal tag consisting of six histidine (6xHis) residues followed by an extended multiple cloning site. The 6xHis tag on the expressed recombinant proteins allows for efficient coupling to Ni2+ affinity resins and purification by single step chromatography (1). As is the case with other protein tag systems (2), this polyhistidine tag can often be cleaved at sites recognized by proteases such as thrombin and enterokinases to isolate the protein of interest (1). Glutathione S-transferase (GST) is another 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 (3-5). The HA tag, derived from an epitope of the influenza hemagglutinin protein, has also been extensively used as a general epitope tag in expression vectors (6), while the Myc epitope tag is routinely used to detect expression of recombinant proteins in bacteria, yeast, insect and mammalian cell systems (7). Finally, the DYKDDDDK peptide has been used extensively as a general epitope tag in expression vectors and consists of only eight amino acids. This peptide can be expressed and detected with the protein of interested as an amino-terminal or carboxy-terminal fusion (8).