The journey from a target gene to purified protein

Many host systems are available including bacteria, yeast, plants, filamentous fungi, insect or mammalian cells grown in culture, and transgenic animals or plants. Each host system has its own advantages and disadvantages, and it is important to consider these before the final selection of a host. After initial screening and identification of optimum expression conditions for your particular protein, you can scale-up the purification process to obtain large amounts of the target protein for downstream applications such as functional and structural studies.

The purification of tagged proteins is relatively simple and saves time due to the high specificity between the tag on the expressed protein and the ligand on the affinity medium. You get high purity in a single step— affinity purification typically gives up to 95% purity. Further purification steps may be necessary if you require greater purity.

Four of the most commonly used purification tags are, polyhistidines (His), glutathione S-Transferase (GST), Strep-tag II and Maltose Binding Protein (MBP).