Epitope tagging is a procedure that inserts a short amino acid sequence into a protein within an expression vector via genetic engineering. Antibodies that recognize the tag can then be used to detect the protein when no antibody to the target protein exists or when the target protein shows low immunogenicity. Such tags can be inserted at the C-terminus, N-terminus or even within the protein itself. Terminal insertion is preferred as internal tags may alter protein function or become buried within the tertiary structure of the protein.
We at Novus Biologicals have a large antibody catalog targeted to epitope tags. They include C-Myc, GFP, HA, DYKDDDDK, and V5 Tag antibody reagents. The V5 tag antibody recognizes the artificially engineered V5 epitope, which is formed of amino acid residues 95-108 of the simian virus 5 RNA polymerase alpha subunit.