Table 3.
Summary of the protein purification tags discussed in this review.
| Tag | Purification Method | Notable Addition(s) | Reference |
|---|---|---|---|
| CBM3 | Microcrystalline cellulase affinity column | Components used are extremely cheap and available Protein tag is very large at 18kDa and may affect structure Used in conjunction with SUMO cleavage leaving no additional overhang |
(Islam et al., 2018) |
| Cysta-tag | Utilises immobilised metal affinity chromatography (IMAC) | His-tag with additional SlCYS8 domain Improved stability with one-step purification |
(Sainsbury et al., 2016) |
| Elastin-like peptides | Heat-mediated purification | ELPs make the RP insoluble at raised temperatures | (Rigano et al., 2013) |
| FSG tag | Tandem affinity purification | Purified by protein G domains | (Jeong et al., 2018) |
| Glutathione S-transferase (GST) | Glutathione | Commonly used but not suitable for every RP | (Kimple et al., 2013) |
| His-tag | IMAC using nickel beads | Purifies endogenous plant proteins containing His-residues in tandem | (Wilken and Nikolov, 2012) |
| HPB-tag | Streptavidin pulldown, cleavage and subsequent HA-tag purification if desired | Synthetically designed tag able to purify low-abundance membrane protein complexes | Qi and Katagiri (2009) |
| Hydrophobin | Aqueous two phase partitioning followed by protein A affinity chromatography | Hydrophobin is fused to Protein A not to the recombinant antibody Only applicable to antibodies |
(Jugler et al., 2020) |
| None – utilise RP | Immunoprecipitation | When no tag is used, and antibodies are raised against the RP itself The generation of specific antibodies is expensive No cleavage of tags is needed Miniaturisation attempts made to improve efficacy |
(Sandison et al., 2010) |
| None – utilises antibody | Protein A affinity chromatography | Only applicable to antibodies but is widely used | (Merlin et al., 2014) |
| Oleosin | Two-phase separation where RP enters lipid phase, and can be cleaved to separate it | Makes RP lipophilic until the oleosin tag is cleaved | (Wilken and Nikolov, 2012) |
| Z-tag | Staphylococcal protein A affinity chromatography | Purified a chloroplast-expressed RP Only applicable to immunoglobulins |
(Daniell et al., 2009) |
| γ-Zein-derived peptides | Cause ER localisation allowing protein to be separated by centrifugation | Similar to localisation motifs such as KDEL | (Joseph et al., 2012). |
This table is not an exhaustive list, but shows a range of examples of purification tags and their respective methods that are available to researchers.