Epitope tags are peptide or protein sequences covalently conjugated, usually to the C- or N-terminus, of a recombinant protein. The addition of epitope tags allows researchers to better identify and purify a target protein within a cell lysate, or localize it and assess its expression in intact cells, when studying transfectants expressing the fusion protein. Therefore, tags can be described as affinity tags, solubilizing tags, epitope tags, reporter tags, or fluorescent tags based on how they are used. These tags can be removed from the fusion protein through enzymatic digestion via TEV protease, thrombin, factor Xa, or enteropeptidase.