Fusion tags in protein purification
The fusion of a small protein or peptide (tag) to the protein of interest is a commonly used method to aid purification of recombinant proteins.
Fusion tags can improve protein expression, stability, resistance to proteolytic degradation and solubility. A wide range of fusion tags are available from small peptides to relatively large proteins, each with its own unique characteristics. Many solubility tags are engineered for use in bacterial expression systems to overcome poor protein solubility.
Fusion Tag | Function | Size (kDa) | Description |
---|---|---|---|
Polyhistidine (e.g. 6xHis, 10xHis) | Affinity | 1-2 | The most commonly used affinity tag, binds to metal ions |
Strep-tag II | Affinity | 1 | High affinity for engineered streptavidin |
Thioredoxin (Trx) | Solubility | 12 | Aids in refolding proteins that require a reducing environment |
Small Ubiquitin-like Modifier (SUMO) | Solubility | 12 | Contains a native cleavage sequence enabling tag removal with SUMO protease |
Glutathione S-transferase (GST) | Solubility, affinity | 26 | High affinity for glutathione, often needs to be removed due to large size |
Maltose Binding Protein (MBP) | Solubility, affinity | 41 | Binds to maltose, often needs to be removed due to large size |