The tag is fused to the N- or C-terminus of the protein of interest, allowing the fusion protein to be purified to near homogeneity in a single-step procedure using a resin with strong binding avidity and selectivity

Introduction Improved purification methods are required for protein structure and function studies, necessitated by growing demands from proteomics, drug development, and biotechnology programs. To simplify purification of recombinant proteins, including many with unknown biochemical properties, several genetically engineered affinity tags, or purification tags, are used. Commonly used tags are polyhistidine (His), glutathione-S-transferase (GST), and the antibody peptide epitope, FLAG (Arnau et al. 2006). The tag is fused to the Nor C-terminus of the protein of interest, allowing the fusion protein to be purified to near homogeneity in a single-step procedure using a resin with strong binding avidity and selectivity to the tag.