Epitope tagging is a powerful and versatile strategy for detecting and purifying proteins expressed by cloned genes. To utilize this feature, protein expression vectors are typically engineered with a nucleotide sequence that encodes the peptide epitope tag. The gene of interest is cloned in-frame relative to the tag and, upon expression, the protein of interest is synthesized as a fusion protein with the peptide tag.

Fusion protein detection and/or purification is mediated by highly specific antibodies to the engineered peptide, thus eliminating the need for antibodies to proteins from each newly cloned gene. Commonly used epitope tags include glutathione-S-transferase (GST), c-myc, 6-histidine (6X-His), FLAG, green fluorescent protein (GFP), maltose binding protein (MBP), influenza A virus haemagglutinin (HA), b-galactosidase, and GAL4. Anti-DDK,4C5 has been successfully used in Western blot and immunofluorescence procedures to detect the presence of fusion proteins containing the epitope tag sequence DYKDDDDK.