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.