Proteins: Affinity Tags


Specific interaction between a protein (or a protein domain) and a ligand allows the protein (or domain) to be linked to a recombinant protein as a fusion partner (affinity tag). This enables the recombinant protein to be purified by affinity chromatography even if it does not naturally have a specific ligand suitable for this process.

Keywords: recombinant protein; purification; affinity tag

Figure 1.

Schematic diagram showing the principle of affinity chromatography. A protein with a high affinity for a ligand can selectively bind to an affinity matrix on which the ligand is immobilized. After washing away the unbound proteins, the protein can be eluted and purified under conditions that disrupt the interaction between the protein and its ligand.

Figure 2.

Chemical structures of the substrates and ligands of affinity tag proteins.

Figure 3.

The scheme of using an affinity tag to purify a recombinant target protein. The gene of a target protein is fused to the gene of an affinity tag. Expression of this fusion gene in cells produces a recombinant fusion protein that can selectively bind to an affinity matrix owing to the presence of the affinity tag in the fusion protein. This allows the fusion protein to be purified by affinity chromatography. After elution of the fusion protein, the target protein can be separated from the affinity tag by a cleavage reaction catalysed by a site‐specific protease.



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Further Reading

LaVallie ER and McCoy JM (1995) Gene fusion expression systems in Escherichia coli. Current Opinion in Biotechnology 6: 501–506.

Paulus H (1998) The chemical basis of protein splicing. Chemical Society Reviews 27: 375–386.

Sassenfeld HM (1990) Engineering proteins for purification. Trends in Biotechnology 8(4): 88–93.

Scopes RK (1994) Protein Purification, 3rd edn. New York: Springer.

Watson JD, Gilman M, Witkowski J and Zoller M (1992) Recombinant DNA, 2nd edn. New York: Scientific American Books.

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Chong, Shaorong(Apr 2001) Proteins: Affinity Tags. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0003141]